Poor or disrupted sleep quality, feeling tired all the time, decreased appetite, joint pain. Training hard is like digging a hole, every stimulus you incur digs a bit deeper and recovery helps you refill the hole.
Of course, the best split is the one you enjoy and allows you to be consistent. :)
I think Push Pull Legs is silly because if you want to hit each body part with a frequency with twice a week, then you'd have to modify push pull legs to 6 days a week or Push Pull Legs Full body (4 days a week) or Push Pull Legs Upper Lower (5 days a week). If you're limited with equipment or a compound lift enjoyer, you really have to make sure your volume, frequency, and intensity are carefully managed when training more than 5-6 days a week or you'll run into recovery problems (either from session to session or your nervous system.) I've always stuck to upper lower (4 days a week)
dont know why i havent before but i went to my first concert in girlmode the other day 
happy pride month gang