Attached Memory Stick

Just taken delivery of my My Cloud 2TB and very happy. Especially as I had read about potential set-up issues on-line. Installation was simple and straightforward.
One quick question though for the experienced users as the WD documentation seems sparse on this subject.
I wish to connect a 128GB USB 3 flash memory stick to the My Cloud USB 3 port. Should the memory stick be formatted NTFS or FAT32 or can it be either? If either then is one format going to give me faster writes times than the other?
Thanks in advance.

Frankly I do not see any differences between each format on the nas itself. You could try both then do a short benchmark on each. Either use dd or hdparm from the ssh terminal.

I have an expendable 32gb usb3 attached to the nas not as storage but as a priority swap partition on top of the existing.