Tiny delay in synth

I know this has been asked 1.7 million times before, probably even by me, but it should be something Cakewalk takes note of because it's just not intuitive, so I'm asking again. They should make this important functionality much clearer.
 
OK, my piano sound has been the ones that came with my Yamaha P-105 keyboard, and that's been okay for a few years. But I want some more flexibility, so I purchased Waves Grand Rhapsody which is a collection of good piano sounds with some more options. But now, there's a nearly imperceptible delay between pressing a key and the sound. It's so tiny that you can't hear it, but when playing the instrument, my pianist brain can tell something's not right. 
 
So, I know there are some preferences I can fiddle with involving buffers and latency settings and whatnot, but (and here's where Cakewalk should make it a lot clearer) I've never really understood those settings, something about buffers. There's one for playback and one for recording, and there are some sorts of trade-offs in terms of latency vs dropouts, depending on your RAM and whatever else.
 
I know many of you reading this know exactly what I'm talking about. I've randomly messed with numbers in preferences, but nothing has made a difference, so I'm not finding it. Help?