I have been booting Mojave AFS on a NVme drive for some time using a Mac Pro 5.1 I have had no issues at all. As I run the public beta program and we are now on 14.2 beta I always do a back up of my boot drive incase of trouble so both drives can boot and then update. I have 2 Mac Pro 5.1 machines. one contains just 1 NVme drive. the other 1 NVme and 1 AHCI drive. In the Mac Pro 5.1 with 2 PCIE cards I have 1 NVme Samsung 970 Evo drive 512g and 1 Samsung ACHI drive 512g so I swap between them as each upgrade or beta is released. Waiting for beta 2 on my main machine with the 2 PCIE drives NVme and AHCI it just would not update to beta 2. yet my other machine updated every time and beta 2 was running fine. So as an experiment as to why the main machine would not update I swaped my boot drive from AHCI to the NVme drive and was greeted by beta 2 update. Again I thought strange as the AHCI drive was a direct clone of the NVme drive. so I looked at the drive info to find the AHCI drive although booting Mojave beta 1 it was in fact Mac OS Extended journaled not AFS format. So although it has booted fine since the beta 1 release with no troubles apple would not allow updates to beta 2 because AFS was not being used. So although you can't install Mojave with out being in AFS you can clone useing super duper to Extended journaled and Mojave will boot fine but receive no updates. one thing I would like to add is that extended journaled booted faster than AFS ? I was always under the impression that Mojave would not run on OS Extended journaled and only on AFS. which is not true as I have now cloned beta 2 to my AHCI drive which is OS extended journaled and again it boots fine with Beta 2. thought others might like to know if they prefer the older file system. just remember no updates while on OS extended journaled.