Depends, what system are you doing this on?
If it's a switch then it'd be pretty easy to see if you're running illegitimate games or cheating online.
If it's a 3DS you're virtually undetectable (unless cheating online).
In any case though whatever you're doing would probably result in a ban, but we need to know what system you're talking about before we can say how likely it would be that you're detected.