MSM on fabric for 1.20.4 You're looking for something where there won't be much, no mechanics, no tech, but maybe a little magic and maybe some design. Well, I've put together this modpack just for the guy behind you, since I don't know how to describe it to you myself, but he'll like it anyway. Anyway, I tried to make it run on my potato laptop, so if you have at least something similar that doesn't even have a GPU, you could run it, maybe, maybe even at 60 fps. I'm shoving 113 mods in there and no let's not talk about the game loading over 200 mods.
There are a lot of boss and weapon mods in the modpack, a bit of degign blocks and a lot of new structures to explore, anyway if you want to throw in something like Biomes O' Plenty and more...
I put a lot in there for optimization, still recommend it at least:
Ryzen 5 5500GT / Intel i5-10400 16GB RAM (at least 12 allocated) I recommend graphics with at least 6gb (I only do it on Intel Iris XE) A mouse and keyboard might also help