RAM usage help

Hello! So I am currently running 16gb (8x2) of DDR4 RAM at 3000mhz. I felt the itch to upgrade, so I bought a 32gb (2x16) set running at 3600mhz.

Basically, my question is would it be better to just swap out the ram sticks (so only run 32gb) or should I throw all 4 in and run at 48gb? Will this affect speeds? Is it better to have more capacity than speeds? Any advice greatly appreciated. Thanks!