DOS and DOS 2 are set in different worlds with completely different game systems so I don't think they would help at all.
BG 1 and 2 are set in the same world but again with very different game systems from 5e.
The Larian system is reasonably close to 5e with a variety of implementation changes but the core concepts and class roles remain. If you haven't played Solasta: Crown of the Magister it is a pretty good 5e implementation.
