Cloning Internal drive to bootable SSD

Has anyone ever done this before? I want to clone my current drive which has 10.14.6 Mojave to an external SSD (actually an NVME drive in an enclosure) and fresh install the newest OS on the macbook. I still want to be able to boot from the SSD though from time to time as if the Macbook is still in Mojave to access older music projects and stuff that I can't necessarily get working with the newest OS. Is there anything besides CCC to use to accomplish this? Am i missing some important info here?