on artstyle:
I think its unfair to say BG1 and 2 didnt have an artstyle. Artstyle is distinct from subject matter. hence why i said Larians artstyle.
Larian might be depicting the sword coast, so the buildings will look relativeley high medieval european and so will the enviroments (i for one would of course argument that ti was more high fatnasy britain, since central europe tends to actually look a bit more rugged, but maybe im just used to the alps)
However, the way these things are depicted is through the artstyle of Larian, it focuses on aspects of that time period and of the lore that larian favors.
Ive brought the example before, but Larian loves Statues.
Their games are full of them, and characters will ofthen evoke Greek statues (maxos and the OCs from OS1 come to mind)
So when they do a Forgotten Realms temple, theyll include a large statue of a Godess.
They also have a certain... height to which they have buildings scale. Its subtle details but you notice them beeing there
Sure, clearly there has to be some degree of artistic consistency across a project, and for smaller developers, the whole studio. When that consistency fails, the result is often not pretty.
In Larian's case, Joachim Vleminckx seems to be the link across DOS1/2 and BG3. He probably likes statues

I do too, for that matter.
There are also some aspects determined by technology. Height is one of those things particularly sensitive to the camera solutions you have, which often carry over from project to project.
There may even be some aspects sensitive to the content creation tools used, but that is probably less likely.
I obviously don't know their output as well as you, so I don't necessarily see all the similarities. But regardless, I like the BG3 environment, as much as I have seen, even if it's slightly strange to see 4000 year old Babylonian mud-brick city walls next to renaissance Italian architecture.