You can get some rather large USB sticks these days. Amazon is awash with 928Gb units for about £10 which are probably not the best. A 256GB or 512GB from a known brand is around £30-50. There are several USB ports on a Pi and you can always boot off a SD card.
Finally, if a network is available then network boot and use NFS or whatever.
The RTC is a cool addition and long overdue. At work I have three Pi 3s with GPS hats and aerials acting as stratum 1 ntp servers. The hats have a RTC included which is handy after a reboot. My use case is "reasonably accurate and stable time" so sub milli second is good enough, I'm not too fussed about nano seconds! I want logs to correlate and desktop clocks to be reliable.
Those are almost certainly 8 to 32GB drives that are modified to report a higher capacity. They are scams that hope your return window expires before you try to load them up with a lot of data. Nobody can profitably manufacture flash drives for less than the wholesale price of the flash chips.
There's no almost about it. They are all scams 100%. The most popular are SD cards with a USB adapter fitted in various housings. The internal adapter or SD cards are modified to do various things like report much larger sizes, allow phantom writes, or even install malware. They can also potentially burn your house down.
FYI I believe all of those ~1TB $10-20 USB drives on amazon are scams- basically set up to trick your computer into showing a terabyte of disk space available, but not actually having that much available if you try to write it all. I was in the market for "largest reasonably priced usb drive" earlier this year and ended up with a 1 TB usb drive for about $80.
I wish some attorney general would buy a bunch of them and then just proceed to sue the shit out of Amazon so hard that Amazon finally gets off it tail and does something.
Flash storage like USB sticks is a crude comparison to an SSD or NVMe with cache and a controller capable of parallel operations.
A USB flash drive is like a dumpster. Big bandwidth when the lid is open but it’s got poor performance for fetching and storing lots of things all the time.
An SSD or NVMe is more like a rolling auto tool chest. Same big metal box, but much more performant for complex and numerous read and write loads.
Or to use a computer analogy: SSD is like a hard disk, USB flash is like a tape drive.
Finally, if a network is available then network boot and use NFS or whatever.
The RTC is a cool addition and long overdue. At work I have three Pi 3s with GPS hats and aerials acting as stratum 1 ntp servers. The hats have a RTC included which is handy after a reboot. My use case is "reasonably accurate and stable time" so sub milli second is good enough, I'm not too fussed about nano seconds! I want logs to correlate and desktop clocks to be reliable.