For me its the map settings before the game starts, the most important settings are:
1. Tech Trading or No Tech Trading (NTT).
2. Pangaea, Continents, Lakes or Arch.
3. Vassals or no vassals.
4. All victory paths enabled or Domination/Conquest/Culture only.
5. Map Speed
6. Map Size/Type
7. Inca doesn't count (your grandma can win with Inca), and Rome will be ignored as well, since Praetorians change how the game is played.
8. You're allowed to reroll coastal starts for civs that start with fishing.
9. Deity is a different game, and is therefore also excluded from options (I don't even think Deity is possible without tech trading lol).
I will assume the following of the above conditions:
No Tech Trading; NOT-Archipelago; No Vassals; Dom/Conq/Culture only; Huge; Marathon.
Exhibit A1: Boudica Domination (Agg/Char)
With no tech trading, Charismatic becomes much stronger. The +2 happiness from Char in the early game in Marathon goes a long a way, because the early game lasts a very long time due to the lack of tech trading. This provides you with a quasi-financial trait by being able to mature two extra cottages per city early than any other civ.
Aggressive is also amplified by NTT. Masses of Shock axes, formation/healing spears and CRIII+Cover Swords from Aggressive can rock the AI civs past 0 AD. Boudica becomes an incredibly stronger leader without Tech Trading enabled. Her units promote insanely fast. Her best strat is to Oracle CoL to chop and whip courthouses as she takes city after city. Her traits are S tier in these map settings.
Exhibit A2: Isabella Spi/Exp
Cover Muskets + Formation Pikes + Supertrebs (make citadels in the settled GG cities) for the first conquest, conquistadors for the next two conquests. Best Civ for Continents with coastal starts, three seafood starts allows you to spam workers, while not needing workers immediately (fishing boats will suffice until you get the food techs), allowing you to go AH before Agriculture to reveal horses.
All remaining exhibits concern Protective civs.
Exhibit B: Charlemagne/Justinian Breakout (Imp/Pro)
Although he's not industrious (reroll starts without stone), you want Great Wall+Mids. Oracle slingshot monarchy and self tech feud and CoL. Bait wars and farm GG's with your long bows and have on city build the Chicen Itza (build all border cities on hills) and use your great spy to steal techs towards his UU. You'll have 10-20 great generals by the time your have Eng. Switch to vassalage and theocracy and enjoy spamming Ultra-Landsknecht. Stay in Representation until Engineering, then go Police State. Use your left over spies to start revolts. Makes lots of catapults prior to Engineering, sac 1-2 cats per city to reduce longbow health. Whip order for captured cities: Walls--> Castle --> Rathaus (bring some works to chop into Rathaus). These cities will cost nigh zero gold to maintain. Your nearest two neighbors are doomed.
Charlemagne will do better than Justinian on Continents, since killing two neighbors on the same continent is essentially winning the game. If there's a runaway civ on the other continent, then his Rathaus allows you to spam Mining Inc/Sushi in every city and outproduce/out tech any AI below deity. This will not work on Lakes (you have no way to put down distant runaway AI civs on Lakes).
On Pangaea/Lakes, Justinian's Super-Cataphracts will be better (same early game strat as Charlemagne) since you play "Whack a Mole" and simply raze each AI civilization in their score order; the combination of Police State + Hippodrome makes war weariness non-existent for 5% or 10 % culture during the razing phase (which will last at least 100-150 turns).
Exhibit C: Sitting Bulb (Phi/Pro)
Get Stonehenge and chop/whip first 5 setters. Make one archer per city while fast teching math, chop the oracle and get metal casting, make forges, bulb machinery, takeover nearest civ with God Tier crossbows (promote cover and formation).
Self tech CoL suring this and chop courthouses, spam farms and switch to caste. Make Chichen Izta again, get Feud, spam longbows, go Eng, get castles, AFK 100-200 turns while longbow turtling, bulb your way to rifles and win the game (most AI civs will still be on Elepult when your draft 12 rifles per turn). Also get Statue of Zeus and GL, each AI will give you tons of gold for peace due the war weariness they'll suffer saccing 50-100 units into 20 Drill IV + Castle + Hill III Longbows (you can easily hold Cuirassiers if things go off script, since Chichen Itza doesn't go obsolete until Rifling.) AI's get literature very late in NNT, so you don't have to tech straight to literature.
Sit in Pacifism + Parthenon until Rifling, then go theocracy for extra oomph to the produced (non-drafted) rifles. Remember that Hill III + Drill IV + CDI superbows + walls/castle/chichen itza can hold off everything including cuirs.
You also want to set up a golden age chain with Sitting Bulb. Chop the Mausoleum, pop your first golden age when taj majal is half-done, taj majl is comples for second golden age, after which you pop a third golden age. During these golden ages you want to switch between caste and slavery, teching towards rifling, while building markets/grocers/banks and universities in each city. In your third golden age you go organized religion to assist, then back to pacifism right before it ends.
Exhibit D: Wang Kon Fin/Pro
The only leader that is guaranteed to win on Lakes Huge with 17 aggressive AI's on Emperor or Immortal.
His UU allows you to hit enemy stacks of doom without needing as many of them. He gets mids and stays in police state spamming his UU until the AI civs have elephants, by which point you should be turtled up with Longbows, riding your cottages to two era military advantage. Best thing to do is to pick a war monger ally (like Shaka or Monty) and declare war on every he asks you to. Never make peace (keep his enemies at war forever for the diplo pints and make sure you share his religion) and request a PA from them after you beeline Communism immediately after writing. Your tech advantage and good diplo will ensure Shaka/Monty accepts your PA.
Once he accepts the PA, end all wars. Spam machine guns and build railroads (use serfdom for railroads on Lakes, otherwise stay in slavery) before your next war too keep his cities safe. Use your financial trait to feed him gold to abuse the AI's unit upgrade advantage. Give him every city you capture, direct his research and attack targets.
Did another AI CIV start to runaway (you should see the signs of a runaway before its too late). Tech to infantry. Pop a golden age, bank 20k gold. Switch to slavery, nationalism, police state, theo. Draft all cites to Six, whipe all remaining pop to 1. March your stack of 300-400 protective draft Infantry to the runaway civ (you should have railroads) and start taking his cities. Keep these cities, because your original cities will be unhappy for the rest of the game. Give your old cities to Shaka/Monty. Right before you units STRIKE out, gift them to Shaka/Monty. Continue to direct his research and attack targets. Use your new cities with no unhappiness to give him air support (fighters and bombers).
Exhibit E: The Epic of Gilgamesh Cre/Pro
Vultures and Ziggurats = two dead neighbors for free (target neighbors with gold/gems to assist in the recovery). Ziggurats = EE, always chop the great wall with Gigs. Yu'll easily have 16-20 zigs pumping espionage points and two great spies before Renaissance era. You also want to chop Stonehenge if you're aiming for a cultural victory (which is assumed for this exhibit).
Since Ziggurats unlock with priesthood, he will always Oracle into Metal Casting in NTT games and bulb machinery. His early xbows aren't as good as sitting bulls, but as protective you can promote them to shock, which is essential since vultures suck at fighting axemen (Shaka/Ragnar/Monty/JC will ruin your day without early xbows) and Praetorians. With the Shock promotion they will attack catapults from behind your walls before axes/swords. Combat promos and shock will knock out chariots. Choose formation for xbows if the Khans are your neighbor.
Self tech castles (engineering) asap to keep your EE going. You want to conquer coastal neighbors since castles and harbors have good synergy (trade routes) and the early forge + Colossus from metal casting slingshot makes coasts desirable as well. The huge early game lead + Protective will let you safely achieve a Cultural Victory.
Exhibit F: Tokugawa Agg/Pro of the English/French/Native America/China
Your drafted Recoats/Musketeers with cover promotions smack AI's with longbows (no siege needed, just a spy or two for the initial city captures).
If your Native America or China, your crossbows will subjugate an entire continent.
Overall, disabling tech trading makes other traits/civs better and also increases the value/important of infrastructure. Protective allows you to use less units to defend while making buildings and bait wars for GG garming.
Aggressive AI increases the value of Protective since you need less defensive units to protect the side of your empire where your main army isn't, and they can one pop walls and castles in captured cities during conquest, which often get counter attacked by third party civs you war dec you in the middle of huge land grab.