I understand this net type sanding disc will work great on drywall compound. Will it work on removing popcorn, assume there is a coat or 2 of primer and/or paint.

We would recommend Granat abrasives for popcorn removal in lower grits (60-80).https://www.festoolproducts.com/accessories/sanders/abrasives/planex-abrasives/festool-granat-for-planex-sanders-40-320-grit-25-pack.html