Seconding grabbing the GOG version. I have a "Civ 4" folder that's fully portable, I can just copy it anywhere and run it, no muss no fuss.
I'm back on Warlords again, because it tends to run better than BTS but mainly cuz I don't really know what the End of Espionage mod really does behind the scenes, if it's breaking anything, etc. There's plenty of depths I've yet to plumb in this iteration so I reckon if I ever get tired of it I can bite the bullet and play the one everybody else plays, but that's a ways off I think.
As for settings it's just no vassals, otherwise all defaults including a random leader for me. Currently playing at Prince but I'll likely move up to Monarch soon. I do have a couple of self-made modifications that don't affect game mechanics in place:
- Music is reverted to how it was in vanilla Civ 4. I never liked how they moved the Classical era music back to Ancient and just crammed in some random Civ 3 tracks for the Classical era.
- A pop-up appears whenever a city grows allowing me to zoom to its city screen if desired. Extremely convenient! You can find that here:
https://forums.civfanatics.com/threads/city-growth-pop-up.691711/
- An "anxiety-free scoreboard" which just takes the little leaderboard, removes the score component, and makes it so the ordering is static, i.e. the leaders don't move around based on their current score. It's useful as a mini-diplo menu and I can still check demos/stats as desired, but I don't get the added per-turn anxiety of "ugh I'm still behind, oh no this guy's climbing," etc.
- Revised year scaling for standard speed. It's the same amount of turns (460) but I made it so turn 100 is 1 AD, turn 190 is 1800 AD, and turn 240 is 1900 AD, meaning the game ends at 2120. So 40/20/2/1 years per turn for 100/90/50/220 turns respectively. It better follows the usual pace of a tech leader in terms of real-world years so people aren't trying to build spaceships in the 1700s or whatever. By turn 260 the tech leader is probably at least firmly in the industrial age so that being the turn of the 20th century makes sense to me. I don't
think this is anything but a cosmetic change, or at least the one game I've finished with this and the one I currently have in progress seem to be normal.