Yes, you can combine two RAM kits with identical specifications on a Ryzen 5900X.
Yes, you can combine two RAM kits with identical specifications on a Ryzen 5900X.
It looks like B-die is quite costly at the moment. You might want to keep what you have for a while. The 3200mhz CL14 or 3600mhz CL16-16-16 should both work with it.