Long answer to question 2, which are the best traits, and further info on what is the best civilization:
When trying to decide who to might be the best, it's important to note what varies between the civilizations: UU, UB, Starting techs, and leader traits.
Let's start with the traits.
Generally, the best traits are typically viewed to be:
Financial (tie for #1) or Philosophical (the other tied for #1).
Organized (the higher the difficulty, the more gold per turn this saves. Also, up to a 50% reduction in build time for Courthouses, Lighthouses and Factories. Due to factory and lighthouse bonuses, is also more powerful on watery maps, where hammers are harder to come by, lighthouses are stronger, and the game is more likely to go until factories)
Industrious (adds to wonders and/or wonder fail gold, and reduces the build time of the second best building, the Forge, in the game by 50%. More powerful on low-hammer maps, like watery maps or ice age maps)
Some people have a major love for spiritual and expansive, but I personally put them as tied at #5, behind any of the ones listed above.
The following leaders have 2 traits composed only of the top 4 traits. 1 "point" will be given for having one of the traits tied for #1. We will also put an asterisk beside anyone with Organized, which notes that it is worth +0.5 if the difficulty is monarch+:
Darius of Persia FIN/ORG 1 point*
Elizabeth of England FIN/PHI 2 points
Franklin Roosevelt of America IND/ORG. 0 points*
Frederick of Germany PHI/ORG 1 point*
Huayna Capac of Inca FIN/IND 1 point
So we have our 5 best leaders. If we pick unrestricted leaders, having one of these people as our leader will probably improve us. If we are not playing unrestricted leaders, then each of these leaders is tied to a specific civilization, with its own UU, UB and starting techs.
So next let's do starting techs. The best starting tech is usually considered to be mining, as it allows you to build mines right away (which are often just as useful as any other improvement for getting settlers and workers out of your first city) AND lets you go straight for bronze working, which allows units (axemen and spearmen), a resource to be revealed (copper), trees to be chopped down, and, most importantly, allows slavery, the most powerful single civic in the game (State Property is a close second, and State property and Caste is actually better than slavery, but that wouldn't be a single civic
). If you cherry-pick starts, then you often look for gems or gold. Either way, you'll need mining. It also allows access to masonry, useful for the Great Lighthouse (a top tier wonder).
The next best tech is much more open for debate.
One thing I can conclusively say, is that Hunting as a starting tech is bad. It is the cheapest of all the starting techs, so you are getting the fewest beakers, and it turns your starting warrior into a starting scout, who can't be used to police your cities (and also, a woodman 2 warrior is often just as fast or faster at exploring). Also, having both spearmen (which require hunting) as well as axemen means you can't build warriors any more, which are a super-cheap way to police core cities (cities away from your borders)
If we want an early religion (which actually isn't that great, but it should mean your starting diplomacy is easier, as you are 1 of the 2 most common religions on most maps, and is important for cultural victories), we want Mysticism. That way our first tech is the religion we want to found. Mysticism can also speed up the Oracle, but this really seems to have less effect than a Gold tile or having-the-right-resources-nearby-so-your-workers-are-always-busy-without-wasting-turns (I'm no master of the intricacies of the Oracle Wonder though).
Whether or not agriculture, or fishing is best depends on your terrain, but usually it is one of those 2 for the number 2 spot, so we can get some food early. Fishing also allows access to early sailing, which can help connect cities without roads (very useful on watery maps to get early trade routes).
So we usually want:
#1 Mining and 1 of Fishing, agriculture
#2 Mining and Mysticism (we want to start an early religion).
Out of our top leaders, we give 1.5 points for mining, 1 point for agriculture or fishing, 0.5 points for mysticism, and -0.5 points for hunting:
Elizabeth of England (Mining, Fishing) Only Elizabeth gets the full 2.5 points.
Darius of Persia: Hunting and Agriculture. 0.5 Points.
Franklin Roosevelt of America: Fishing and agriculture. 2 points
Frederick of Germany: Hunting and Mining. 1 Point
Huayna of the Incas: Agriculture and mysticism. 1.5 Points
Total so far:
Elizabeth: 4.5 points
Huayna: 2.5 Points
Franklin Roosevelt: 2 points*
Frederick: 2 Points*
Darius 1.5*
Next we look at UU's.
They are scored as follows:
Era they appear: +1 points if your UU is ancient age, +0.5 if it is classical, 0 if it is medieval, -0.5 if it renaissance, -1 if it is industrial, -1.5 if it is modern. Obviously, this assumes an ancient age start. If you started later, these numbers would completely change. Having praetorian's as your UU would be a bad thing if you started in the modern age where prateorian's are long obsolete
Additional Strength given (really subjective, I won't lie): -0.5 to +1.5. Yes, some UU's are crappier than their normal counterparts.
Additional bonus if the unit is very common or strong on it own: up to +1
Darius:
Immortals+1 for age, +1 for strength, +0 for base unit being common-ish, but weak, with a reasonable, but certainly not long window
Elizabeth: (BTS! In vanilla, the
Redcoats are uber-powerful, but in BTS they have been very notably weakened!): -0.5 for era, +0.5 for additional strength, +0.5 for strength and commonality of base unit. +0.5 total.
Franklin Roosevelt:
Navy Seals-1.5 for era, +0.5 for bonus strength, + 0 for base unit being okay. -1 total.
Frederick:
Panzer-1.5 for era, +0 for additional strength (just bring an anti-tank infantry!), +0.5 for strength and commonality of the base unit. -1 total.
Huayna Capac:
Quechua+1.5 for era. +0.75 for strength, but +1.25 strength if the difficulty is monarch+ and the AI starts with archers; again, will be denoted by an asterisk. -0.5 for the fact that the base unit is the weakest unit in the game, with the shortest effective window. +2 total.
Running total:
Elizabeth: 5 points
Huayna: 4.5 Points*
Darius 3.5 points*
Franklin Roosevelt: 1 point*
Frederick: 1 Point*
Lastly, we look at the UB's. I use the same criteria as the UU's essentially.
Era they appear: +1 points if your UB is ancient age, +0.5 if it is classical, 0 if it is medieval, -0.5 if it renaissance, -1 if it is industrial, -1.5 if it is modern.
Additional Strength given (really subjective, I won't lie): 0 to +1.5. Minimum of 0 instead of negative, as there are no UB's that are worse than their counterparts.
Additional bonus if the building is very common or strong on it own: up to +0.5
Darius:
Apothecary. Era: 0. +0.75 for building strength. It's main purpose is health, and it gives even more health. +0.5 for commonality and strength of the base building. +1.25
Elizabeth:
Stock Exchange. Era: -0.5. Additional strength, +0.75. +0.25 for strength of base building. +0.5 total.
Franklin Roosevelt:
Mall -1.5 for era, +1.25 for bonus strength, -0.25 for building being okay, but basically completely skip-able, even when you have access to it. -0.5
Frederick:
Assembly Plant-1.5 for era, 0 for additional strength (just cheaper if you have coal, which is already copied by anyone with Organized), +0.5 for strength and commonality of the base unit. -1. total.
strength-wise, but not commonly used. -1 total.
Huayna Capac:
Terrace+1.5 for era. +0.75 for strength (allows you to completely skip monuments in all your cities). +1 for the fact that the base building is the most common building in the game, necessary in every city worth settling. +3.25 total.
Final Total
Huayna: 7.75 Points *
Elizabeth: 5.5 points
Darius 4.75 points *
Franklin Roosevelt: 0.5 points *
Frederick: -0.25 Points *
* denotes adding +0.5 when playing monarch plus. For Huayna, this is from his UU finding its ideal target and being able to rush more easily than ever. For the others, it is from organized saving more gold on higher difficulties.
Which leaves
Huayna Capac of the Incans as the best of the standard-rules leader-and-civilzation combos, and Elizabeth of England and Darius of Persia as the second and third respectively. If you are playing with Unrestricted Leaders, Elizabeth and Darius are the two top leaders for just about any civilization, with Huayna and Frederick close behind.
Other eat my GP farm ! haha 
And if you have city with just some 3 mines and everything else coastal, than Dike + Moai + Heroic Epic + Military Academy + (Drydock) + Forge + Factory + Coal plant.. I guess that can give some 45-50 base hammers.. after +%, something bigger for sure 
