Internal Boot FTW!!!
I finally completed the transition to internal boot, and overall the process went smoothly. Once I reviewed the documentation, the workflow was straightforward. The only part I would approach differently next time is moving data off the cache pool relying on the Unraid mover added unnecessary time. Using an alternate transfer method would have been more efficient.
In total, the migration took roughly eight hours, primarily due to relocating about 520 GB of data (and we all know how Unraid performs with large quantities of small files). That portion alone consumed around four hours.
After the initial transfer, I ran the Internal Boot Wizard, rebooted, and formatted my two 2 TB NVMe drives for a mirrored configuration. Once the pool was initialized, I moved everything back and performed multiple boot‑cycle tests at various times throughout the weekend. Unraid booted cleanly every time.
No more “unable to enumerate USB device” errors or swapping USB ports — the internal boot setup completely resolved those issues.