Power Pop is a term, much like Northern Soul, that unfortunately frames music in a "does it fit?/ it doesn't fit" game of flora and fauna that often gets in the way of enjoying good music in the first place.
For example, there's alot of (mostly 90s) groups I love that take some cues from power pop that just aren't power pop, bands like Redd Kross, The Pooh Sticks, Sloan, Teenage Fanclub, Tsar, The Wannadies and Silver Sun. But I would take any of them over the average revivalist group who look the part.
But I digress.
Grab the Poptopia comps that Rhino put out. Grab that Nerves reissue. You can find those Marshall Crenshaw records in any dollar bin and they're great. For newer stuff, get the Tranzmitors record.
As for a Who inroads, I firmly believe the gateway rests in the visual: start with The Kids Are Alright and worry about the records later.