I was originally classically trained, and it is true that classical teachers say you should play with your wrist as straight as possible, with totally in line being the best option. To do this you have to pretty much play with the guitar on your chin and your fretting hand at eye level. This approach has advantages in reach at lower frets, but is near impossible up the top end of the neck without moving the guitar to your forehead...

It's a compromise - obviously, if you try to shred while playing with your guitar hanging around your knees, you're putting more stress on your wrist and tendons and increasing the likelihood of injury.

If you're not in pain doing whatever you are doing, you're OK as far as I'm concerned. You don't get carpel tunnel overnight....