O removedor de cutículas é indispensável?

Or is polimento the nails with a 240 buffer enough too?

A cuticle remover is preferable, or even a careful removal with a cutícula tool. It is skin (non-living) and is too soft to be efficiently removed with a buffer. Plus, the placa ungueal could be over buffed. Just remember to remove it in the appropriate way and make sure the nail plate is clean and dry.