An easy way to detect cheaters is to look at overall accuracy as some aggregate metric of deviation from 'optimal' (as per the engine(s) used). This could just

An easy way to detect cheaters is to look at overall accuracy as some aggregate metric of deviation from 'optimal' (as per the engine(s) used). This could just be a average of squares of centipawns lost per move, or classifying moves like how chess.com does (brilliant/best/excellent/good/inaccuracy/mistake/blunder/missed-win) and then looking at average distributions from this.