The three I watch are trainer tips, mystic7 and straight up knives.
I also watch prodigies nation occasionally...He's the best battler I've seen on YouTube. He has a few guides to soloing level 3 raid bosses that I found very helpful. I wish he would get out of his car and play more, but good info.
If you want to watch a guy using a tracker, but not providing any insight or commentary on the game, that's jonnoplays. Not worth your time imo.
I've tried watching reversal a few times, but not a lot
Another guy that does good videos, but quit playing/uploading Pokémon go for a while is Lachlan. His recent Japan videos were all really good. He's based in Australia, so it's a unique perspective.