Johnny91 That's an interesting question, which I can't answer in detail unfortunately. No doubt nvme will be faster than SSD, but how much difference, I can't really say. Disk performance is definitely important when running Files Gallery, because PHP needs to read the file system when generating folder views, and also loop through all dirs on disk when creating the menu.
It would be faster when generating non-cached views and menu, but provide little benefit with already cached items. It wouldn't offer any benefit for resizing images (CPU) or resized image cache. The nvme would need to be connected to mainboard without any bottleneck (eg. external drive), as this could block any performance benefit with fast PHP server I/O. It also depends on the server setup and the amount of traffic (simultaneous visitors).
In reality, I am guessing the difference will be negligible. For sure, both SSD and nvme provide huge benefit vs traditional mechanical HDD drives.