I have no experience with D&D5 in P&P, but as far as I know:
1. No, absolutely not. All this physics stuff is Larian style. Its not in BG1 or BG2 and its not in P&P D&D.
2. How many items you get during adventuring depends upon the GM. Players can craft magic items themselves in P&P and the BG3 style items are very different from BG1, BG2 or P&P anyway.
3. That depends upon the individual player. Also, in P&P D&D you have to meet minimum requirements to be allowed to multiclass to a class (like Str 13 or Dex for a Fighter, Wis 13 for a Cleric, both Wis 13 and Cha 13 for a Druid, etc).
4. In real D&D you can write scrolls and craft potions yourself, instead of having to rely on finding them in shops. Neither BG1, nor BG2, nor BG3 reach in any way the flexibility you have in this regard in P&P. BG1 and BG2 also know wands, not sure why BG3 doesnt know them.
5. No. In BG3, respec is a fix for newbies who are unfamiliar with D&D and ended up with a weak build, and it increases replayability because you can change your companions completely around.
6. The implementation of Haste in BG3 is simply incorrect.
7. I dont do stealth but its a lot less time wasting in P&P compared to computer games.
