Spec jumping will give you a good idea where most people are at any given time. You'll see me hop from player to player when I'm dead to get a general feel, then watch an individual player to observe their behaviour. It's not rocket science. And tbh if you look out for wall hacks they always seem to try to shoot spam spots that aren't spam-able, and the classic staring through walls at targets miles away whilst omitting the basics of cornering or keeping their crosshair aimed correctly....once you've played the game enough you also learn that the glock doesn't go through walls either.
If you honestly think I was hacking, by all means use this demo as your proof and create a topic about me instead.