Can you really upgrade the RAM in the M1 2020 Mac Mini to 64 Gigs?
Memory on the Apple Silicon M1 chips is part of the chip. There is no slot to add memory on the M1 based Air, Pro or mini.
I would not mistake an 8 GB RAM Air, Pro or Mini for anything but a beast of a workstation for many tasks. Real world benchmarks are showing them doing tasks dramatically faster than 12 core Mac Pro with 32 GB of RAM.

https://twitter.com/cocoalabs/status/1330199233090244615

Pick any ten apps you want to start and race the entry level Air with any Mac of your choosing - iMac Pro, Mac Pro, or an 8 core MacBook Pro - there are only few specialized tasks where the Air is slower.