BAT mod changes the trade routes (not BUG), to basically undo the double rounding that BTS does.
BUG = just user interface and quality of life changes (fist on leaderboard when AI is plotting)
BAT = BUG + graphics changes (and more precise trade routes), this is a community flavor mod
BUFFY = BUG + anti-cheat measures that we use for Hall of Fame and other competitive games. No trade route rounding.
There's also "Better AI" mod that can be tacked onto any of these that makes minor AI changes but no game rule changes.
The BAT changes to trade routes are good, the only problem is the result is a slight buff to the Great Lighthouse, which is already arguably the best wonder.
Only gameplay change we might have between BUFFY and what you play is around overflow hammers. I don't remember exactly where the last BTS patch landed, but our community decided that excess overflow hammers (more than the cost of the unit being finished) would convert to gold. This was to strike a balance between hammers disappearing without warning the player and preventing unlimited overflow being stacked to finish space race parts the turn they're available.
The Hall of Fame is basically our verified records list using BUFFY mod.
https://hof.civfanatics.net/civ4/index.php There's a list of settings that are allowed or not allowed, and there's slots for competing for any record possible (game speed, size, difficulty, and victory type). It's not everyone's cup of tea because of the sheer volume of records and that any competitive one is going to require maximizing all the settings to your advantage. For instance, most forum games are going to have normal barbarian activity with no huts and no events, while most HoF records are going to have barbs turned off and huts and events turned on, to give the player every possible advantage. HoF players generally use MapFinder to sort through thousands of maps to find candidates with the best starting position.
Most deity players don't count Apostolic Palace or culture wins as beating the map. I personally don't count UN victories, and others feel strongly that nukes should be taboo. GotM and HoF competitions have slots for every victory.
In a HA rush we generally advise building a handful of chariots over stables in the run-up to building HAs. Exceptions exist (like for Mongolia), but the idea is you don't need the full 6 strength of an HA to mop up a unit that's already been hurt. A classic "snowball" argument where getting out a few chariots allows you to attack earlier and more opportunistically.
The flip side of your idea that attacking earlier is safer is that the earlier you're attacking the fewer units you're using and the more "bad luck" can cost you the game. In other words, I'd expect successful HA rushes to outperform successful construction attacks, but I'd expect HA rushes to have a slightly higher fail rate than construction attacks, all things equal.
Cuirassier rush takes advantage of great people bulbing and tech trading to gain a decisive tech advantage even on a poor map. Meta is Aesthetics (tech trade) -> Literature (with option of building Great Library and National Epic) -> Music for free Great Artist -> bulb Philosophy (for Pacifism) -> double bulb education and taking Nationalism or Military Tradition from Liberalism. Cuirassiers can stomp AIs double your size because the most resistance the AI can offer at the time is longbows/pikes. This is why I think your concern over losing control of the early game is overblown: runaway AIs usually aren't out of control until they get rifling or defense pacts. This is generally only a problem if they're on another continent.