From what you've said about being a completionist, this kind of goes along with changes I'd been making over the last few RPGs I've played and more so in BG3. A while ago games often expected you to loot *everything*, but that seems to be less the case now. Maybe after those spoof live action videos of Link from The Legend of Zelda running into someone's house, smashing all their pottery and running away. Partly because BG3 doesn't reward searching everything, but also because it's unrealistic for me as the player character, I just *don't* search everything. You can kind of cheat by holding down some key (alt for me) and it puts labels on containers that have something in them.
Same goes for everything else like books, dialogue and sidequests. First of all, you're supposed to enjoy playing a game, it shouldn't feel like a job that's given you a list of tasks. But secondly, BG3 in particular is designed so that you can't see everything in a single playthrough: for example, you can't kill the goblins and raid the Emerald Grove in the same game. By deliberately leaving some missions undone, you have more stuff to enjoy if you do play it again, but even if you don't you'll still have got loads out of it. The approach I use is I think about how much my character would want to do a mission (or speak to someone, etc.), against the amount of effort it'll take. So if it's on my way, I'm more likely to do it. But there were a few missions, sometimes that I even started, that I later realised I'd need to go a long distance out of my way and that it wouldn't appeal to my character. So, I ignored it. I can do is as someone else.
Biggest lessons I learnt that I can think of are to quicksave often, because if you get a TPK you can easily lose 30-60 minutes of playtime to an autosave; and to go with the flow sometimes if you fail a roll, and see what happens. I think there was another one, but I can't remember it now. I also enjoyed thoroughly roleplaying the party (especially my own characters), with their own personalities, but I understand that's not everyone's cup of tea
