Gotek floppy disk emulator can not be used on an Amiga computer without modding it. Luckily it is not hard to change the firmware on the device to be able to boot ADF images from an USB drive.
There is plenty of free software available for the 8-bit Atari XL / XE computers online in the form of ATR files. These are image files created from the physical disks. A huge database can be found on Atari Mania website.
To create single sided disks on a PC (Windows XP) we will need a floppy drive that is connected to the FDD controller. The tests that I have done with USB floppy drive failed. It simply did not want to recognise single sided (360K) formatted floppy disks.
MSX2 Philips NMS 8250 computer has a build-in double density (DD) floppy drive. There a various sites on the internet where you can download floppy disk images. For example on planetemu website you can browse MSX2 various disks section and "télécharger", as the site is in french language, and means "download".