Ok, specifically Skyrim inspired open world is what I meant.
With BG you had a sizable overworld that was nonetheless split into smaller isometrically viewed chunks.
BG1 seems to have been conceived as essentially a single chunk (or maybe two, with the city separate) and then split up, my guess is for technical reasons. The maps mostly fit together if you splice them together, to the extent that shadows of large objects will show up in neighbouring maps.
(The Cloakwood maps don't really seem to fit, or the firewine bridge)
DAI open world isn't really very Skyrim like. Its not a single overworld, and it doesn't have loads and loads of dungeons. Its more of an MMO structure to be honest