How willl a Mac Mini's SSD effect the maximum process size when use swap?
macOS does not limit the maximum process size (i.e. working set) according to total RAM and a fixed proportion of available disk. This is 100% not the case in any way at all.

You can set arbitrary limits on process size using the "ulimit" command in the Terminal, those are however limits chosen by the user - and thus can be changed as need be.

There are ofcourse actual, "physical" limits of a process size given by the hardware. Contrary to common belief, it is not actually possible for an ordinary 64-bit system to have processes that address 2^64-1 bytes of RAM. On macOS (and Windows other systems) processes are actually limited to 2^48-1 bytes instead. I.e. a given pointer only has 48 bits that are actually significant.

There are paging techniques to counter this, but in practice no ordinary program employs them.

In addition to the physical limits, there are other limits you'll run into. If you have meaningful data in RAM, the system needs somewhere to store it. The total RAM installed on the system as well as the free disk space available for swapping becomes a limit.

Note that this is not a fixed limit in any way. If your RAM contents are compressable (i.e. for example if it contains many repeated bytes), then you'll be able to have extremely large process sizes without problems. Much more than you have physical RAM and swap space.