I've got the Futaba 7ch 2.4GHz FASST (T7CAH?)
Anyway, any switch (and there's lots of them) can be assigned to any channel for rate switching. So you can have just the one switch do everything.

You can also assign a rate change for when the stick moves beyond a certain deflection, so that rate changes are automatically selected.

Mixing is a not quite so simple. There are undocumented preferences such as Ch 1 and Ch6 for dual aileron and Ch2 and Ch5 for dual elevator. If, asI did, you use different channels for mixing these functions, the trim only works on one surface, so putting aileron trim in causes a pitch change and putting in elevator trim causes a roll. I'm sure there's a book somewhere that has it all explained, but why isn't it in the manual?
Oh, and while I'm ranting, the front of the TX isn't fuel proof. Fuel has got under the chroming and has caused blisters.