Running processes at startup vs startUpList, which one first?

It depends on two things:

a) is the process at a higher, the same or lower priority than the process running the start-up code?  Only if it has the same priority is there an issue.  If it is higher it will run first.  If it is lower it will run last.  But if the process had a higher priority and was runnable then it would have prevented the process attempting to snapshot from snapshotting in the first lace.

b) if it is the same it will not run until the start up code does a wait or a Processor yield.

Snapshot writes the current system state to a file.  That includes runnable processes.  No magic happens here.  The current process *must* have been the process that did the snapshot.  The current process *must* have been the highest priority runnable process not waiting to run when the snapshot occurred.  Snapshot is *not* equivalent to Processor yield.