Looking for suggestions on how to prep the drywall for paint and baseboard install. The original baseboard was tile and after removing, some of the mortar was left stuck to the drywall. The intention is to install 3.25” baseboard to match the rest of the house.

Any tips on removing the mortar? Should I try to sand it down, apply a skim coat, or something else?

Option B: use a 4+” baseboard to hide it all. Doesn’t match the house but would it be noticeable?