Morning, and thanks for your questions!
These are questions, which to be honest never came up when I was first writing this how to, but they are perfectly valid and reasonable to ask.
I'll answer what I can for you based on my experiences with STFMs and STEs, and if I'm wrong, then hopefully one of the good folks on here can jump on and correct me.
With regards to Gotek not working with TOS 1.0, it's difficult to comment as I have never tested on a version of TOS that old, but I would expect that this shouldn't be a problem as the Gotek presents itself as a floppy drive. There are issues with hard drives under TOS v1.0 if I recall, but this is a different matter entirely and shouldn't affect Gotek use.
In all honesty I would suggest for the best compatibility and use of your STF, that you should upgrade to TOS 1.04 anyway, you can find it here: https://www.exxoshost.co.uk/atari/last/storenew/#0033
, just scroll through to find the one for you.
As for 1.44MB or 720KB, I never considered this to be a problem and certainly didn't specify a 720kb device only when I was buying.
The models I've used are marked SFRC922C and SRFC922D, which as far as I'm aware are both 1.44MB capable devices. Ultimately, it's the firmware that determines what the drive can/can't read, and I've used Goteks with FlashFloppy firmware on both STs and an Amiga 1200 without any issues.(Well other than the cheap ass USB sticks I used. Use decent ones and you'll be fine).
I've only ever used normal ST images, so I can't comment on 360KB or 800KB, as I just haven't tried. I'd expect that 360KB would be fine and that 800KB should also work based on the fact it does for the A1200. Again, I'm happy to be corrected if somebody has better knowledge than me.
Be aware that FlashFloppy and HxC firmware doesn't support .STX images (See here: http://pasti.fxatari.com/)
, which are intended as images for the preservation of software, not as images for use with floppy emulators. HxC did get as far as an alpha support version for STX images if I recall, but then it was dropped. I'm pretty sure you can't use .MSA images either, but it is relatively easy to convert these to .ST format, there are utilities to be found here: http://msaconverter.free.fr/index-uk.html
If you have a Windows 2000 or above PC with a proper floppy disk drive (Not USB), then you can also use FloImg (See here: http://atari.8bitchip.info/floimgd.php
) to read/write and image disks.
Hopefully some of that is of use to you!