Indeed, 'Power Chord' is a colloquial and excessive term, because we get only two notes so it is not a chord according to the standard definition of a music chord.
But now, it has entered in the usual language, so....

Re the 'X1+8 chord', sometines noted X8 : this 'chord' is often used in etheral movie music for examples.
Not yet available as RealTracks, but you can get it easy with MIDI : writing the full parts (2 notes) or playing with MIDI harmonies in the Melody or Soloist tracks.

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