well a chord has at least 3 notes, but a power chord has two, the root, and the fifth. When it has 3 notes, a chord is called a triad.

If you use a scale one fret higher, what you get is another scale (but not another type of scale)... For example, an A minor pentatonic played one fret higher is an A# minor pentatonic
You can play the two scales in a row if the tune you are playing tells you to do so... In a blues progression, playing the two scales in a row might sound like you're adding tension, but it will rapidly sound like you're playing your licks one fret too high...
Some Jazz cats use the one fret lower approach to sound "out", they first play a lick one fret too low, then play the lick in the right key... Sounds hip!!!