How will you be using it?
As a backup device that you write to weekly or less often?
Or will you be using it every day for whatever reason?
The more often you use it, the more you might get annoyed if it were only an average speed drive.
If you were to write to it less often, maybe you should be more concerned about durability, price, warranty.
Ordinary USB flash drives scare me because they are held together with glue and can come apart in your hands with very little abuse.
Here is an alternative:
You could buy an enclosure roughly 1 inch wide and 5 inches long that would attach by cable to a USB port on your PC. You could then buy a very fast NVME SSD to fit inside that enclosure....whatever brand, model, and size you want. The cables with the enclosures are typically about a foot long. The whole thing functions as a high capacity and very high speed USB flash drive.
I rigged one up myself about a year ago, using a Western Digital SN550 of 500 GB capacity inside the enclosure. Works flawlessly and quite durable. Total cost about 85 dollars (25 for the enclosure and 60 for the SSD). I could replace the 500 GB drive with a 1 or 2 TB drive if necessary. Buy the size you need.
If you get an ordinary USB flash drive, I'd certainly be sure it had no moving parts, such as a slider mechanism.