I currently have 4x 4GB @3000Mhz, if I swap out one of the buses for x2 16GB @3200Mhz, will it slow them down to 3000Mhz even though they are in a separate bus?
I've just seen so many people have issues mixing anything ddr4 that I'd be wary about it working correctly. Definitely try it if you have it, but don't count on it working right.
Your question is not very clear but if you are asking if you can run dual channel memory at different speeds in each channel, then the answer is no. Both channels must match exactly, either 3000MHz or 3200MHz, not both at the same time.
I read that mixing is fine as long as you're okay with using the slower of the two's clock. I'll probably just end up only using the x2 16GB @ 3200Mhz and just take out the other 2 4G
I've just seen so many people have issues mixing anything ddr4 that I'd be wary about it working correctly. Definitely try it if you have it, but don't count on it working right.