PCIe3x1 is still double the bandwidth of a SATA drive, and both 2.5 inch and M.2 SATA drives cost just as much as an NVMe drive. There's just no reason to get a 2.5 inch if you CAN use NVMe. And while the adapters SHOULD work with any generation, having it specifically stated by the company is nice, and it's possible for them to cut the quality just enough to make using it in a higher generation than rated to result in just enough reduction in things like signal quality to cause problems.
I don't use queue depths of 32 when I benchmark my drives. I use 4 which is the default in ATTO, and I still get blazingly fast speeds. The absolute peak speeds in marketing obviously use the most optimized testing on the best boards possible, but even in less optimal testing NVMe is much faster than SATA. Benchmarks of course don't mean anything in the real world, they're just an indicator of what COULD happen. While most activity is small random I/O, NVMe does make systems boot faster than SATA, and anybody coming here probably does more than just loading MS Word and MS Edge and will have points where they are transferring a lot of data like games, and when the cost difference is tiny or non-existent, why would you NOT get the faster model that will at least improve performance noticeably sometimes?