Personal preference. Ive always turned my knights inwards since I was a kid similar to Kasparov, Carlsen does the same. Anand points his knights forward. Do what thou wilt.
What is Kasparov doing with his knights?

That's how they look on diagrams and computers. I personally don't pay attention to that when playing OTB.
https://www.youtube.com/watch?v=s7xCc3Qjfis&t=5m
Before every game, the knights are turned. Is there a reason for this?