Help on mixers!

I am new to PX4, but i need to start on a difficult and no so well documented subject.
I have a new design Evtol tilting quadrotor that is a scale model of a new concept. The model is ready to fly but i have to program the controller in my case a Holybro px4.
I plan to start flighing it at the beginning as a quadcopter but front rotor are much smaller then rear ones ,so i had to learn somehow how to write a custom mixer geometry file and rebuild the code.
I just made a very short take off and i found that the model was pitching forward but i could control the attitude with the stick. I think was not so bad!
But ,now, since customisation is not well documented, i need to ask few questions:

  1. Toml files are useful for rotor mixer autogeneration but are equivalent to a set of mixer created manually one for each motor .Using as coefficient the vaulues of the generated matrix the result should be the same?

2.I dont understand how each mixer line in the mix file is associated with one phisical output connector on holybro power module: what is the meaning of PWM_OUT 1234 ? Channel on main.mix are associated with FMU output pins and the ones on aux.mix with the aux pins ?Is the number of the pin the order of the mixers files lines?

  1. I think mixer should be as easy to modify as possible: i have found the way of copying a mixer in the controller SD, this is quite useful. But best should be to modify mixers during flight ! This may essential when we start tilting the rotors and go in transition.
    Is this possible?