Question

Being able to control studio one’s mixer input gain with Console 1.

Answer 1

I'm running Studio One 4.6.2  and I have two places to set input gain for each input channel:

These appear to operate independently of one another.  Note that you can put plugins right on the input channel, before the signal gets to the mixer as well as on the mixer channel.  e.g. maybe you need to compress the signal on some input before you can use it at all, if its just too hot.