Guitar technique is also about control between applying pressure to the frets when playing something and releasing the pressure when moving to something else, particularly when moving up and down the fret-board.
When playing power chords I sometimes notice beginners seem to drag their finger(s) up and down the fret-board from one chord to the next. This is because they aren’t releasing the pressure quickly enough before moving to the next chord and there’s too much tension in the hand. To improve on this I get them to play slowly and break the process down to separate movements of on / off / move / on / off / move etc. It may seem a bit mechanical compared to how when played within music it sounds flowing, but the process is the same, albeit at different speed.
Below is a basic power chord exercise; be aware of the process of “on” when playing the chord and “off” when releasing the pressure before changing to the next. Start slowly at first, using a metronome to stay in time can help. The rhythms are simple so you can strum each chord downward leaving you to concentrate on the fretting hand.