Ciao Leo,
and welcome aboard! A long long time ago, I had the opportunity to try my brother's ZX81. Then arrived his Spectrum 48K (with its games!), upgraded to Spectrum+. Finally, I got the wonderful QL!

I'm not a Gotek owner, but if I understood correctly you must prepare the Usb drive connecting it to PC and using the provided Gotek software. Unless you use a Goldcard, probably you'll have to set as 720K disk. Then the pendrive can be recognised as floppy disc(s). You also must set the Gotek as dr...

Here is a PDF containing detailed info about different Spectrum RGB pinouts:

https://mts.speccy.cz/doc/128_rgb.pdf

No! The pinout is different

The drive needed an external power supply, as we thought the QL PSU was not powerful to power the 3.5" floppy drive. The end result worked well, but only a single drive, no real expansion for multiple floppy drives. I think it would be more feasible to install a floppy drive emulator. Somethin...

Cristian wrote:Check ebay: there are several serial mice, both old and new

But be careful: not all the serial mice are compatible with a bbQL. I tried some before find the right one.

Check ebay: there are several serial mice, both old and new

A picture of the switch would be useful. Anyway, some Miracle interfaces (for example (S)Goldcard) allows up to 4 drives, so it may be normal to find drives with more than 2 positions

Andrew wrote:there is not enough room in the QL case

For a normal floppy drive. Have you tried also a smaller external drive? Just for information