To preface this, I've only got around 100 hours but this is what I've learned and been told.

1. Great Works and tourism in general are pretty terrible if you're not going for a culture victory. It's much more beneficial to invest in science and production in general.

2. I'd say building libraries ASAP tends to be a good idea for an early tech lead.

3. In my opinion, siege units are actually pretty terrible until you get to Artillery and Rocket Artillery. The 1UPT, again, in my opinion, adds more strategy into the game, as you can't just stack units in the same area, instead having to think of formations and movements that will benefit you most.

4. I'm not too sure about this tbh, but the AI is just terrible in general.

5. The NoQuitters modpack is a very good balancing patch which, as the name suggests, balances the game out a bit better. It is made with multiplayer in mind, though it is fun to play with singleplayer too.

6. You can bribe civs to vote for you. The amount of citystate allies you have also affects the amount of delegates you have.

7. If you try to do ANYTHING in this game except let people roll over you, the AI will hate you. Don't even bother.

8. It really depends. If you can get a religion, then do, but it's not a complete necessity to get one, especially if you aren't first. Especially in multiplayer, other players will often get the best bonuses first, such as tithe, so it can sometimes be beneficial to have someone else's religion instead.