No.

You need to choose SFPs that are not vendor-specific (i.e., without special firmware for Cisco, Brocade, Intel, etc.) and support the correct wavelength for multimode operation, which for RME is 1310nm (not 850nm).

If all RME devices used SFPs, 850nm might be an option. However, devices like the UFX+, UFX III, and HDSPe MADI [FX], etc
have fixed transceivers using 1310nm.
Mixing wavelengths of 850nm and 1310nm between devices is not possible!
Therefore, all RME devices must use 1310nm.
Why is 1310nm being used? According to my research, 1310nm has lower attenuation over longer distances, enabling a 2 km range, which is likely the reason why multimode with 1310nm is being used.

Do not mix multimode with single-mode. Multimode uses LEDs and fiber cables with a core diameter of 50–100 micrometers to support multiple light beams (hence the name multimode). Single-mode uses lasers with more energy, with only one focused beam, requiring a core diameter of only 8–10 micrometers.

Best get the one from RME, then you have no hassles sending back and forth if you should pick the wrong one.

You know what Original Cisco SFP cost alone (without cables and adapters) and this is not one of the most expensive ones:
https://www.bechtle.com/de-en/shop/cisc … -712589--p

With RME you also get an adapter cable LC-SC and SC/SC connector to be able to extend an optical cable, which may well be necessary. In this respect, I think the offer is still quite fair. It should be clear that RME cannot pass this on 1:1 at pure material costs ...

You can try this one as an alternative:
https://www.fs.com/de/products/37324.html

I would stay with optical, because it gives you galvanic isolation, get OM4 cables in violet looks better than aquamarine or orange (OM3). OM4 is not more expensive. If you have in house cabling check whether its OM3 or OM4. You should not have OM3 and OM4 mixed between two devices.

You can get simplex cables but you can also use duplex cables, then you have always one fiber as a reserve.

UFX III and 12Mic have both Steady Clock FS, so both can be a perfect clock slave.

See my blog article about further information on clock synch including links to RME YouTube videos about SteadyClock FS:
: https://www.tonstudio-forum.de/blog/ent … ios-en-de/

I would make UFX III to clock master and clock synch through MADI optical.
Use 96k MADI frame size on both devices to support smooth change between single and double speed.

True, but galvanic isolation is a general advantage to prevent that any potential hum spreads through the setup.
Doesn't cost that much more.

Maybe a bad example, but satellite connection from TV introduced hum to all HiFi components.
Since using optical SPDIF exclusively between components, the problem is gone.