I assume you're talking about getting an AIO rather than going for a custom loop. Any 240/280/360mm radiator AIO is going to allow you to show off your RGB memory, the block will literally just cover the CPU socket.
Looking at the NR200 case you might be pretty space constrained for radiators, I personally always use radiators for exhausts so you're not filling your case with warm air so I'd be tempted to put it at the top as an exhaust.