Given you have the RPi and UPS ordered, there’s no convincing reason to change HW, wasting your invest.
Keep the system on SD and use a simple stick or the SSD for the backup, but enable ZRAM to mitigate wearout.
Sure you can also move to SSD but then you a) need to know how to do that AND b) need to have another SSD ready on standby in case yours breaks (as you should have a spare RPi ready at hand).
