I ran 10 different configurations with my WD SN850 2TB on Windows 11. Interestingly increasing the fragment size to 512 KiB actually reduces the sequential read speed, although it increases the sequential write speed. Bumping it up to 1024 KiB recovers the read speed back to 256 KiB levels, while further boosting the write speed. Going up to 2048 KiB doesn't seem to have an impact.