Service you offer is very specific and i'm not sure there are many people who own crypto and play chess. Anyway, you probably want to add some detail (such as supported cryptocurrency and how you handle network TX fee) to make your service looks more convincing.
Good question.
We will be using chess.com who is very good with detecting bots.
Furthermore I will not allow games longer than 10mins a side. It is very hard to cheat when you have a tight time limit.
Are you aware of Stockfish (probably most popular chess engine)? If someone install that on their device, they could switch window/app (between chess.com and stockfish) and able to see good moves from the engine in less than a minute.