As far as I know the pvp is optional. you get egg fragments for winning and those can turn into eggs if you get enough. Reviews seem to quote around 50+ hours for the main story, but there's also post game - I don't know how much of that factored into the "50+" timeframe for the reviewers, if at all.
I've been playing pretty slowly today.
Seriously the animation work is on-point. I mean, the main games are stellar too, so I assume they were able to pull from that database or have some of that talent work on this.
Seriously, fuck Z moves from Sun/Moon. They ain't got shit on the ride moves in this game. Not only that, but you have to earn the right to use the fuckers. Build that meter up, then call them shots to get to level 3 and lay down the PAIN anime style.