Hello adelaideviewer,
Yes -- you still need to be able to able to load the whole sample set into RAM.
macOS is also rather memory-hungry, generally needing about a third of the physical RAM for itself. Hence I'd recommend deciding on how much memory you think you'll need for the largest sample set that you plan to use during the lifespan of the machine, then multiplying that be at least 1.5 to determine the minimum amount of physical RAM to buy with the machine. (With Apple's current/recent Macs you can't add more RAM later.)
In order to be able to use a reasonable range of current/recent sample sets, I'd certainly go for a Mac with at least 64 GB of RAM if feasible. (Even more would allow for a greater degree of future-proofing.)