With the latter, I meant that the perspective would switch between the two, third person and top down, not that the perspective would literally be some combination of the two.
Well, if we go by the video of them talking about engines, apparently the DOS2 Definitive Ed. is the basis for whatever BG3 will look like, so it will more or less be like that.
And that pretty much rules out an Action RPG like Dragon's Dogma.
Not necessarily. I'm not seeing why Divinity 2 (IMHO Dragon's Dogma is a lot like it) couldn't be done with the OS2 engine, for example. I'd wondered about that at the time of DOS and it was apparently impractical at the time but perhaps not so much now; but this is conjecture on my part and I don't really know.
The engine does have some awkward limitations as of OS2 though, perhaps partly with the isometric setting being an excuse, but a particularly serious problem is that the pathing is only two-dimensional, like the original Doom. Though it's possible to give the illusion of 3D using raised areas of terrain, it isn't. I guess it depends how deeply that design decision is embedded.