The SafeTech disk creation should indeed only write two files to the disk (v5 atleast). One of these files contains a small OS which will load the safetech app, hence you will only see two small files on the disk / usb drive instead, rather than a bunch of files as you had in v4..
In addition -- yes, you can use either a floppy or a USB drive (latter will only go for v5).
An alternative method for creating the disk, in the situation that you can not connect your USB drive to your safeboot server, is to copy the 2 files (safetech.rtb and bootdisk.exe) from the SbAdmin/SafeTech dir on your server to your local machine, and execute it locally by the dos prompt:
bootdisk.exe safetech.rtb f: (assuming that your f: drive is your usb drive).
In the case that the OS doesnt boot from the USB drive, it might very well be that the USB drive itself can not be made bootable unfortunately.. This goes beyond the scopes of SafeTech. Suggestible then is to use a floppy.