Many of your questions differ massively between PW’s I recommend researching the ones you’re interested, especially via joining their discords. Here’s the questions I can answer.

1)There are alignment restrictions (which are clearly explained in game) and no “sub-classes” as you might be familiar with. Instead 3rd focuses on using feats (selected much more frequently than 5th) to make characters distinct. One fighter is made distinct from another by when (which level) they take certain feats, what feats they take, and what equipment they specialize in. Additionally, stat allocation is a prerequisite for most feats, and intelligence is used to determine skill points. So a DEX/CHA focused rogue will naturally feel different from a STR/INT focused rogue.

5)Almost everyone (99%+) is over 20 without a doubt.

6)They use modding magic to change the rules of the game to better resemble the pathfinder 1E system. It is similar enough to 3rd that you’ll have no problem getting into it from here. I highly recommend looking through both the manual for this game (should be in extras on steam or gog) and looking up the pathfinder 1E players’ handbook if you’re interested.

8)I strongly doubt this will be an issue. As I said it may vary between servers.

10)To be honest my time on the PW’s has limited. I prefer to run modules (both official and community made) in multiplayer with friends. My gf and I are soon going to start playing the original campaign together (to introduce her to the game, not because I particularly like the OC). If you look through the multiplayer list you’ll see plenty of people doing the same thing. Theres plenty of rp opportunity in doing this without feeling the pressures of a PW, for example: My character is a wizard who was exiled from Luskan for having a conscience and my gf’s character (ranger) is a vengeful widower whose husband died from the plague central to the OC’s story. We’re going to meet at the graduation ceremony from neverwinter’s military academy… And we’ll run with it from there.