PDW - i'd go with a compensator. that thing has some goofy left-right recoil (.15-.35) and compensator will get it down to .11-.25 so it will be a bit more manageable. the recoil up isn't bad (.26) compared to say the ACE 23 (.36) so with the proper tap fire you shouldn't need a muzzle break or angeld/folding grip. the compensator will also decrease your spread per bullet significantly making long range and hip spray battles more win-able. an ergo/vertical grip will also decrease your ADS spread again making long range and hip spray battles more win-able. make sure your in a good spot to reload, they are pretty long, 3.6 empty and 2.5 with one bullet left. be ready to pistol swap if you get caught with your pants down.
for the G36 i'd personally use a suppressor with a potato/stubby grip to increase hip spray accuracy.
what type of game mode are you trying to optimize for and why do you want to use those guns?