Full duplex ?!? Aren’t you using the UR22 ASIO driver?
The best settings for recording are the lowest latency/smallest buffer you can get away with without experiencing problems.
Playback isn’t so critical. I’ll usually record at 64-128 and playback/mix at whatever I need to get smooth performance. Usually 1024 for mixing. It all depends on what your system can handle given your current project demands.