I actually added that guy who's 2nd account got a VACation, however I never got a chance to play with him, so can't comment on that xD
I actually managed to reach LE recently after playing CSGO competitive mode seriously about 2-3 games a day for 2 months. After playing for a long amount of time you can sorta tell whether the player is hacking.
And yes there's alot of hackers in CSGO. It depends on what kind of hacks they use, and how smart/efficient they conceal it. But overall you still have dumb hackers who go full retard and get themselves caught or their skill is not that good to fully utilize the hacks (e.g wallhack)
On a side note, reaching SMFC/GE is really no joke. It requires very high skill, perfect accuracy, and insane game/situational awareness. And you need the correct tools too, mechanical keyboard, good mouse, good headset to listen to directional sound, 120~144hz monitor. I'm using a 60Hz monitor and very often, I feel that my monitor is too slow to keep up and that got me killed and losing the game everytime