NV+ v1, Can/should I boot it without drives??

Rebuild it how? The OS partitions and data on on the 500 GB drives. If NAS-A boots with the 2TB drives, then it should boot with the 500 GB drives.

I agree, if it boots with one set, it should boot with another set. At least that's how I understood things to work.
Am I correct in thinking, at boot the NAS does not care what drives are in it? It will boot and then read the partition info from the second set of drives?
Rebuild meaning NV+A will be a new config from its original with new 2TB drives, restarting via reset button, let it do its thing.

BTW, knowing the OS in the flash is not very useful, when disks are inserted, the NAS boots from the hard drive.

So with no drives the unit is basically "stupid"? Is this 'boot data' spread across all four drives, or just one? If so, which one? Trying to understand the boot process.
From above:

...provide the steps it goes through when the NV+ boots. Kind of a "this happens, then this, then this....and if this doesn't happen then this is displayed, etc."

Or a link with this info would be nice to read through.

When you installed the 500 GB drives in NV-a, was the NAS powered down?

Yes. Both were shut down, slot assingments kept the same.

My new RAM arrived today so I will play with that too.