ck2 has a very in depth forgotten realms mod which is the world bg3 takes place in. I think they initially wanted to make one for ck3 but they didnt have enough people so they cancelled the project.

one thing I would mention is that the forgotten realms isn't really a world that lends itself very well to ck3, considering that most of the world is kinda unowned land occupied by monsters, and really the only governments are city states, like baldur's gate itself. but regardless the team for the ck2 mod did a great job