I presume that the SSD wouldn't consume enough power to make this unusable, but SSDs tend to not retain data when they're sitting on a shelf. Additionally, I believe USB-C 3.0's speeds are slower than SATA, although I could be wrong on that one.
SSDs and USBs use the same NAND flash technology to store data. Neither has a battery, so there is absolutely no power, and therefore no data transfer going on here.
NAND Flash can degrade over time, but so can any other form of data storage. It has nothing to do with being unpowered.
Fun fact: SSDs rely on quantum mechanics to store data. They're really fun to read about, and not even slightly intuitive.
If you're doing regular backups, an SSD would be totally fine I think, since it's getting power reapplied to it regularly. maybe use ZFS or a filesystem that protects against bit rot?
USB 3.0 caps out at 5Gbit per second, which is 1Gbit short of Gen3 SATA. USB 3.1 bumps up to 10Gbit which would mean likely no bandwidth limitation if you were to run a 3.1 capable adapter and machine, or if you were at 3.0, it would be a relatively small loss. Also, anecdotally, I've spun up 16 TB Seagate hard disks (spinning rust) with USB to SATA adapters, so I imagine it would work and wouldn't be as cursed as it looks :3
edit: picture looks like an SSD with a USB port, not a SATA SSD. My above rant applies to SATA SSDs, not USB SSDs like the above.
Thats a samsung T series (hard to say which model probably T5) i have been using them for backups for a few years now. They have USB 3.1 and write at ~300 MB/s. Very light which is nice for travel and if you format it correctly it plays nice with your phone too