I don't think I lose power on lower kicks targeted to legs and hip area. I don't ever do head kicks because I am short and stocky and am a far better with my hands.
I would assume high kicks ya you would lose power since it would be harder to balance and pretty much impossible to keep your hands up leaning back and extending your hip all the way out. But for my style I don't do high kicks so not a big deal for me.
Wraps are a good idea... I forgot mine on saturday and my wrist is killing me from a poorly executed right hook... It is a great workout though.... I am addicted to murdering the heavy bag....
yeah why wouldnt you wear wraps.. the last thing i would want is an injury before a big tournament because i didnt wrap my hands while hitting the bag..