Ah, RME will say that USB 2.0 can handle up to 100 channels. I use the Babyface though and it works a little differently. UFX has I think 30 channels input and output - total 60 channels - should have no problem with USB if newer type controllers on your motherboard. IC7H I think at least, but some computers are different, but anything newer should work fine.
Firewire400 has 400Mb/sec whatever it is, and USB 2 has 48Mb/sec. Usuallyfirewire takes a TI controller and anyway, there are no firewire ports on a computer (windowsOS) usually anyway, so USB2 is always used.
And new version 1.036 drivers from RME just came out - mainly because of Windows 8.1 and that is about it.
TotalMixFX program is not an input gain on my Babyface, it is a listening and monitoring program. That is all.
If you do not have an adequate signal into like my Babyface, then TotalMixFX will show that, or even the DAW program. I am not sure about the others, but I sure you can read about any of them over at the RME website.
Just Do Not Use Hosa Cables on any input Neutrick combo whatever connector. Those cables will get stuck in there, and it becomes a mess to remove them without breaking the connector. Usually the unit has to be taken apart to remove them. Use cables that are rounded more than more triangle shaped on the tip connection, that is where the Hosa cables fail and can wreck the connection into the unit.Otherwise you will have trouble with those cables.