That’s a false dichotomy. There is a third possibly:
He is an extremely talented and skilled chess player, who will resort to cheating to beat people at his level, using it sparingly.
Yes, we know this from cheating in other competitive sports, offline and online, though obviously there's more cheating online. Most speedrunners who have cheated well enough to secure a first place on a leaderboard, have been very, very good players even without cheating.