It seems the read/write speeds of of built-in SSD in these latest Macs are so fast that "virtual memory" (aka "memory swapping") is now a thing once again (previously popularised by the DEC VAX 11/780 series of computers back around the '80s). Virtual memory is storage media (e.g. HDD or SSD) used as if it was RAM.
A pro video editor has reported Mac M1 tests in which substantial amounts of memory swapping (as logged by Activity Monitor) made little if any practical difference to the total time taken by various editing tasks, when compared to another M1 doing the same tasks but with maxed-out RAM so no memory swapping happened.
I've not yet seen read- and write-cycle times officially specified for the SSD in the Mac Studio, but it's being suggested that these speeds are not radically dissimilar to RAM speed - and RAM cycles are astoundingly fast in the Mac Studio! A staggering feat of high-tech and engineering R&D!
However, as one who may be buying a Mac Studio in the not too distant future, I see some reasons for caution:-
1. Virtual memory operations involve writing to SSD as if it was RAM, whenever free RAM space is not immediately available. No matter the speed, the fact is that writing to SSD brings it "one step closer to death" (to borrow a Pink Floyd lyric). SSD lifetime expectancy depends mainly on Total Bytes Written (TBW).
2. All of the Mac Studio's RAM is now general purpose. Neither graphics nor AI processes have their own dedicated RAM. Perhaps Apple are counting on virtual memory to diminish the impact of hard-to-predict heavy and/or complex system usage momentarily running out of available RAM.
3. So, generally speaking, the more that virtual memory has to be used by the system in order to get around shortage of RAM, the shorter the SSD's life expectancy will become. And conversely, the more RAM the new Mac has, the better conserved SSD life expectancy is likely to be. Virtual memory was not particularly good as a general panacea back in the '80s; in the Mac Studio it appears to be a significantly better panacea, but with a somewhat narrower scope of applicability.
4. In the Mac Studio, neither RAM nor internal SSD can be expanded later; nor is replacing dead internal SSD a matter of swapping plugin modules. Moreover, Mike Bombich (proprietor of Carbon Copy Cloner) reports that a part of Mac Studio's built-in SSD is always involved in booting from an external drive. Hence when built-in SSD dies, so does the possibility of booting from an external backup.
5. External SSDs can be used with a Mac Studio but are limited to Thunderbolt 4 speed of 40 Gbits/sec (5000 MBytes/s), which I don't think is in the same ballpark as Mac Studio's built-in SSD speed. If MacOS treats an external SSD boot drive as fair game for virtual memory operation, I'd expect to see significant performance slowdowns whenever a lot of memory swaps occur in the external boot SSD.
Choosing the Mac Studio RAM and SSD configuration when buying new appears to be far more critical than ever before, especially for those of us who require several TBytes of storage for sample libraries alone. Aiming for the very best possible return on investment in terms of economy versus system performance, flexibility and lifespan, is now, it seems to me, a bit of a nightmare.