China DOS Union

The old computer is on DOS system.
I want to buy a USB flash drive (with write protection) for the old computer. It is used for Win95 boot, multi-DOS version boot, and transferring files with XP computers.
I don't know whether to choose USB 2.0 flash drive or USB 3.0 flash drive.
16G or 32G, which one to choose?

Mainly messing around under DOS 3.3, DOS 5.0, DOS 6.0.
I'm afraid that if I buy a USB 3.0, class 10 flash drive, it won't work with DOS.

Attachment:

CPU type Intel Celeron D 335, 2800 MHz (21 x 133)
Motherboard name QDI BA1 / BA1/GV / P4I845GL / PlatiniX
Motherboard chipset Intel Brookdale-G i845GEV
System memory 247 MB (PC2700 DDR SDRAM)

The USB I'm using is USB2.0 4G.
I suggest that for USB drives larger than 2G, use FAT32 instead of FAT16, otherwise data corruption may occur.

Because the partition table can only be FAT16, and the maximum management of the hard disk is only 2G, so U disks are generally sufficient at 4-8G. I always use 16M and 32M U disks.