If they dont offer 32 and 64 MB memory options, its a non-starter for me. Anything with a Pro label capped at 16Mb of RAM is sad. I use a 2012 iMac with 32Mb of Ram that is now not capable of running Big Sur, and really wanted to move to a new Apple Silicon Mac. Why should Mac Mini, and iMac users (our only non Mac Pro options for desktop machines) have to downgrade from up to 64Mb?
All that having been said, I also really appreciate the approach of integrating the memory on the SOC from a security point of view as well as the SOC controlled security of the SSD Storage. I am a big fan of better security and OS sandboxing of memory to prevent apps from accessing other app or OS data. So I am not criticizing the design to be clear.
I hope Apple will comment on expanded memory options we can expect in the future.