Which fingers to use for holding/muting the strings on PC with the open bass note. So many different variations each with its own problems.
PC = power chord, yes?
So we're talking about (for example):
6th string root - 2 4 4 X X X
5th string root - X 2 4 4 X X
Were you asking about 4th string root, too? - X X 2 4 5 x
This is how I play them:
6th string root is easy - 1st finger on 6th string; 2nd & 3rd on 5th & 4th strings (or barre with 2nd, 3rd or 4th finger). 1st finger mutes strings 3, 2 & 1.
5th string root - same, but the tip of 1st finger and/or thumb of left hand mutes the 6th string. 1st finger mutes strings 2 & 1.
4th string root - 1st finger on 4th string; 2nd & 3rd on 2nd & 3rd strings. The tip of 1st finger mutes 5th string & thumb of left hand mutes the 6th string (maybe combined with the 'heel' of my picking hand). I usually mute the 1st string by letting my 3rd finger lean over.
Don't worry too much about which way you play them, just find something that works to start with. Later on you will inevitably use different fingerings depending on context.