Keep Dolp saves separate from Vanilla saves, you can use your vanilla save to continue from your base game progress in Dolp. Just don't load Dolp saves in base game.
I do, so far I did not encounter any bug.
It does add quite a lot of stuff but I suggest reading their wiki because a lot of changes are not really explained in game and even when they are the explanation is rather vague or not helpful at all.
I prefer the combat in DoL+.