Unless one can accept multi-second delay after pressing Play or Pause, you cannot have too large a buffer with RAAT playback. Lumin RAAT buffer is tuned for good UI response while handling a reasonable amount of irregular network activity with a wired network. (Our native OpenHome implementation for using Lumin app, however, uses as a much larger buffer.)
Having WiFi connection from the Roon Core is a bad idea, not saying it does not work for everyone, but certainly some people’s WiFi setup won’t be good enough.