OK.
I'll be lazy and ask the idiot question.
What's the short story/explanation about Zwiftpower? Does it help with sorting out who to race with and how do I sign up?
Most Zwift races transfer their results to ZP, which does the "final" classification/ranking, taking into account, what trainer people uses (smart, non-smart etc.), heart rate (not using a HR-strap gets you disqualified in many races) and manyh other things.
You sign up to Strava and ZwiftPower and link those two, as they use real life data to see, if your Zwift performance is wrong compared to real life (ie. you cheat or use a faulty trainer). Then on your Zwift profile, you have to opt-in to ZwiftPower, to allow them to get your race data etc. (because of GDPR).