I'm coming from a P6 Pro and it's definitely a lot better, but not gone. I was browsing the web on Firefox for like an hour on a drive, and running kinestop to prevent car sickness. I also had poor cell signal (mountains). My P8 Pro did end up thermal throttling and I wasn't even charging. Had to take the case off to cool it.
I can, however, charge while running Android Auto which is not something I could do with the P6 Pro