Because my rear Guide brake seemingly auto adjust its bite point (which is pretty deathy) I am swapping them out for brakes made by Shimano.

Do I need new post mount adapters for the fork and frame (both post mount), or will the ones that came with the bike work?

Probably assuming your Guide were post mount but some types are incompatible with each other but it is rare.
Some Hope ones for example wont work with others and vice versa

Ok. Sounds like I probably don’t need them. Thanks 😀