GoKawiilUSB 3.0 was the first major successor to USB 2.0. It bumped the maximum theoretical transfer speed to 5 Gbps, compared to the earlier standard's 480 Mbps. From there, USB naming got complicated. The two following standards were initially called USB 3.1 and USB 3.2, but everything was retroactively changed to use "Gen" names.
The group behind USB now recommends using the max transfer rate for clarity, instead of "USB 3.2" followed by the generation — these cap out at 5 Gbps, 10 Gbps or 20 Gbps. Thus, if you see "USB 3.2" on a box, it doesn't necessarily indicate how fast that drive will be. You'll need to check the transfer rate elsewhere in the specs.
USB-C doesn't fix this problem either. USB-C is a connector type, not a performance promise, so USB-C devices can run at USB 2.0 speeds. What USB-C can give you is convenience. Having both USB-A and USB-C connectors on a single drive makes it easier to switch between older PCs and newer laptops, tablets or phones without having to carry an adapter around.
It's the actual read and write speeds that count. For example, Kingston rates its DataTraveler Max at up to 1,000 MB/s reads and 900 MB/s writes. In a 10GB transfer test, Tom's Hardware measured Samsung's cheaper Fit Plus at 319.7 MB/s reads and just 58.4 MB/s writes. That gap won't matter much when copying a PDF, but a folder full of 4K video is a different matter.
A USB driver's controller handles tasks such as error correction and write management, while the flash memory itself also influences performance. Unfortunately, flash drive manufacturers don't always disclose enough about those components to make them easy to compare. Actual speeds can also drop during long transfers, so anyone regularly moving hundreds of gigabytes should pay special attention to sustained write performance rather than assuming the largest number on the package is what you'll always get.