Mac Mini M4 - Virtual Work

• No, you cannot use a SSD as a direct substitute for RAM.
• Mac minis with M4 Pro chips have Thunderbolt 5 ports, and OWC has a Thunderbolt 5 SSD which they claim can hit speeds of over 6000 MB/s, faster than any Thunderbolt 3/4 or USB4 40 Gbps drive.
• If you were get a M4 Pro Mac mini, install macOS on such an external SSD, and boot from the external drive, that would presumably speed things up on those occasions where macOS swaps out data to the startup drive (rather than to compressed RAM). That might let you put more of a load on the virtual memory system – although I still do not think that it would be a substitute for having an adequate amount of RAM.

There's another consideration. Virtual machines use the same type of machine language as the host CPU. If you're planning on running instances of Intel distributions of Windows or Intel distributions of Linux on a M4 Mac mini, that is not going to fly. There is an ARM version of Windows 11, and there may be ARM versions of some Linux distros – but if you've tied yourself to Intel-based systems (as corporate IT departments often do), a M4 Mac mini would not be suitable for your virtualization project at all.

No, macOS does not support using an external drive for virtual memory, at least not by any method I've ever encountered. It's designed to use the boot drive and I know of no way to redirect that. So if you wish to purchase a new Mac mini, you will need to purchase enough internal storage to allow a generous amount for VM. And of course you'll want to purchase the mini with as much RAM as budget allows so as to keep the system out of VM swapping as much as possible.

Regards.