Two microphones

You can use any number of mic configurations. You could even run into a mixer to allow for different volume levels from each specific mic. You would then run into the return per manual description.

Yes, it works - be aware of phase cancelation effects when using two or more mic's.

I used two different type mics close together when doing my JTM30 and it turned out very well. My logic was that combining the different frequency characteristics of the mics would lead to a more balanced overall sound.

Many of us have used a Condenser + Dynamic mic combination. It works just as well as when used for recording.

I think all of us are answering your first question (about using a small mixer).

In terms of your second question:
I don't know that it is possible to use the line in as a second input when profiling, but that is something that has been suggested as a new feature.

Andy suggested I put my TLM103 about 8" from the grill and my SM57 on the grill, I did that at a 45 degree angle about an inch in and pointing towards the edge of the cone.

I go through 2 separate preamps (because they are both only 1 channel), a UA LA610 which is a warm tube preamp for the Nuemann and has a compressor to tame it (I also used the 15db pad) and a Chameleon 7602 which is a solid state Neve clone for the Shure.

I got what I thought were my best profiles that way, than using single mics or going further away with the TLM (which gave me phase problems)

I combined the signal and went in on one line input on the KPA. Do a few different profiles to see if you have phase issues.

Or submit them to the Forum for feedback.

You can do that only with a mixer, Alt Input is not for profiling.

Give it a try with the Behringer. You don´t need a high end mixer for this profiling stuff. Be creative and play with tone controls and different blendings of the mics. I got some of my best cab profiles with quite extreme mixer eq settings.

I would also use headphones from the mixer while you play with separate microphone placement as you can really hear the difference with only slight changes.