With a real tube amp, which has consistent characteristics going out to FOH all night long, you can absolutely be sure that what you’re hearing on stage is **closer** to what the audience is hearing. Not exact of course, but reasonably close.
This is not the case if you are using a Kemper through a traditional guitar cab, but sending studio profiles of different amps, with different cab emulations, out to FOH. It will still sound good to the audience, but it will be much less consistent and you will have less of an idea of what they’re hearing.
And that’s why people use FRFR speakers, to get **closer** to what is happening out front. Unfortunately my experiments with that setup leave me wanting, and I’m unwilling at this point to keep throwing money at the problem.