mostly it's same minus sidequests (totally stupid mostly) which had nothing to do with mainstory, yes could control mia couple times.
they dropped rpgm for a reason, they could have added sidequests and mia control on renpy if wanted but didn't.
they have 3 teams making games and mia stopped being moneymaker long ago.
You can play Mia half of the game - the 2 MC's are been switched all the time - first you do some story with Mia's brother then the game switch them and you start play the game with Mia and do choices with her - this is all till the end of all 3 chapters and it's not just a couple of times!
They decide to start making RenPy because is much more easy to do it instead of RPGM which takes a lot more time and they obviously decide to focus only on Mia's brother because that way they can work more easy at few games,otherwise they can't focus all the time on making a few games since it will took them too much time to make the two view of the story in Mia - Mia's view by playing it and doing choices with her and then the view of hers brother and to keep switch them all the time in every next chapter (and let's not forget the sidequests too) - this is too hard to do it and it took a lot more of time if you don't know and obviously at least for now all games of INCETON are only with one MC! Not every developer can do that to switch two MC's in one game all the time like is for example in "Mad Turn" or " Happy Marriage" (which are Unity ones) or some other games where you play with two MC's all the time! Even if you have a few teams that doesn't mean all teams are working only on the story of one game - actually every team work on a different game story - for example one team works on "Inside Jennifer",the second works on Limits of Sky,the third works on "Living with Mia/Summer with Mia",another team work on Echoes of Lust,another one on another game and at least for now they all follow one kind of playing model and doing choices in every game and that's probably the other reason why they decide to keep only with one MC in Mia's story,so they can follow the type of "model" what they do till now in all their games! You know that some company(because INCETON is company) are following a speciffic model to make their games,right? If you don't then now you already know it! Right now they are focused of making the story of a few other games and that's why they stop for now with Mia - and because they see that making it playing only with her brother loose them a lot of fans too but that's other story!