booting yes
installing on SSD no
for some strange reason it will not boot pfSense without the USB plugged into it. Also having just the USB will not boot pfSense either.
However I did multiple test booting of the BIOS to see whether storage devices get changed in boot order.
They do not. the BIOS will assign in order …
PCEngine: APU1C4
Compact Flash
SSD
USB "A" - top
USB "B" - bottom
1. USB MSC Drive Multiple Card Reader 1.00
2. AHCI/0: SuperSSpeed mSATA SSD 16GB ATA-7 Hard-Disk (15258 M
3. USB MSC Drive SanDisk U3 Cruzer Micro 4.04
4. DVD/CD [USB MSC Drive SanDisk U3 Cruzer Micro 4.04]
5. Payload [setup]
6. Payload [memtest]
And yes, if any body asks the SSD has the new firmware.