Functionally, your road shorts are perfectly fine for MTB.

Baggies (chamois liner with a baggie shell) are mostly a fashion thing. And that’s fine - I tend to wear them for MTB myself. But in my experience there is zero functional benefit.

Baggies have pockets, which can be nice.

in theory they might give some more protection, but in practice I’ve used both for almost 20 years and have not noticed a difference in this regard.