I've been looking to help him as well, I'm the buddy hes been trying to play with.
Some details I feel he neglected to mention.
This is Enhanced Edition, and hes on windows 10.
We tested both multiplayer and single player, new save and old one.
It is unique to this game, as he is been able to run more demanding games at max or near max.
As he should from the linked parts list.
I'm really at a loss, he did find a thread that suggested .ini editing some texture streaming options that didnt seem to fix the issue.