All 4TB would be available under Windows 9x. The limit is 16TiB.
NUSB is fine. I doubt you will find a Manufacturer Driver for any of these enclosures.
I have a special Win98 opsys without nusb, for testing manufacturer-provided drivers under Win98. The enclosure does work fine under Win98 with the Win98 driver v1.04 by JMicron, with a Pioneer BD-R 203 SATA blu-ray burner inside, so a SATA HDD should work fine also. The exe installer file of the JMicron driver v1.04 has a time-stamp of 8-Dec-2006, so I am a little skeptical about its ability to "Support 4K sectors HDD command". Does nusb require an update to handle HDDs >2TB?
I supply Partitioning and Formatting tools as part of the TBPlus Package. Single Partitions up to 8TiB are fully compatable.
I can't say if a particular Driver will work without actually testing them. The Lexar based drivers, I offer free on my website, work. The USBSTOR files from Windows ME work fine. I use only part of nusb but I don't think it needs any updates.
The TBPLUS Package patches Kernel files to add the support.