I had a 5600x on a b450 board with Kingston pc3600 too. I had no problems running xmp profiles and optimized defaults. If cool & quiet was enabled by default then I didn’t mess with it.
I rarely use suspend or hibernate, and I don’t encrypt my drives, so I can’t speak to those issues. But even though you say you don’t need the speed, I think you’ll be very pleased with this upgrade if you go through with it.