Exactly. Fast then fizzes out then slow on lots of small files. Best on large files. Doesn't make sense. Used same sticks both cases and is very consistent. The usb sticks I have are reliable and are usb 3.0 plugged in usb 3.0 ports.
I don't like this how it works.
Good suggestion on NVME to usb 3.0 adapter in the future. For now, I'll try a small old SSD in another usb 3.0 external box.
Update:
Tried again, got consistent 150MB/s as as low as 30MB/s but I still see: small files writes fell to 3MB/s still if too many but happens quicker.
Using a old Intel 710 100GB SATA SSD in a reused seagate external box (was 2TB SMR). Better. I have many 100GB 710 for other uses also intended for windows 98se. Intel 710 is designed for high usage. Same as intel 320 but 710 has 1 more chip to usual 10 NAND ICs and 20GB reserved for reallocation, good turnkey for ease of use with good life.
Back in the day when OCZ was making usb sticks, I found one that was best, dual channel using 2 NAND ICs in parallel to speed up. Got great results. Is there good brand that is based on this design and for usb 3.0?
Cheers,
Great Northern aka Canada.