I don't think we are the soul, rather we just control it.
Think of it from a narrative standpoint: some of the choices are from Kris giving the option... but the other options, can we really say they're OUR options?
Our options are more actual actions at best, us going moving closer to Ralsei, us going back to get the ribbon in Tenna's game, etc etc etc.
That's the player doing stuff.
But when we have to make a choice (such as Proceed or Me) that's not us, because we didn't make up that option.
I don't think it will ever be explained in the game (much like Chara wasn't really explained in Undertale) but to me the soul is not us even though we're controlling it, the soul is its own character.
So we control the soul and both it and Kris gives us options, with the soul being more "in control" the further we go into routes like Snowgrave.

That's what makes sense to me and why Kris is so hostile to "us", he has no reason to be hostile to the player but he has all the reason to be hostile to a soul that already proved itself to be a problem.
It would be more likely that's the case in my opinion and why sometimes we have choices that Kris wouldn't pick: why would he give us the choice to say "I will never play the piano again" if that's not what he wanted us to say?
Why would he give us the choice to pray to Noelle?
Why even give us the choice to pray?
The soul is its own entity and not necessarily a benevolent one, that may very well be the "demon" Kris and Catty summoned, we just established connection with it.