My rudder pedals are painted and I've flown the airplane with just a painted floor and with a rubber mat/carpet piece installed there. No difference, no slipping nothing. I don't think functionally it matters much one way or another.
As far as the adjustable pedal assembly, I don't think that matters much either. Once you find your position you won't be moving them anyway unless you have multiple people flying the plane.
N229Z - RV-8 - Flying - Livin' the dream!