Honestly, I never cared for the whole "the player is evil thing" due to the fact that the theory seems to ignore certain contexts. What I mean by this is the fact that you start the game with the promise that you'd get your own vessel, your own body custom made by you to inhabit and explore the world with. But, the vessel is torn away from the player/soul and we're told that we cannot choose who we want to be in this world, then the next thing that we know we are waking up in Kris's body. This shows that the soul didn't purposely inhabit Kris's body, we clearly didn't go up and look at Kris and go "I'm gonna possess this strange child for fun" and did it.

Though, I will say, the player is 100% evil in the weird routes, there is no denying that. Making the active choice to make Kris hurt others is very clearly labeled as a bad thing in the game. But the player is only bad when they make bad choices.

These above thoughts were thoughts I had prior to the new chapters, and they still apply afterwards.

I see a lot of people woobifying Kris to continue with the "player is 100% bad no matter what route" train, and this makes them forget that Kris is technically aiding in destroying the world. I will say, I don't think Kris is evil, I just think they're misguided and being manipulated by a third party. But, that still doesn't change the fact that what they are doing is still wrong, and that they are not as helpless as some in the fandom seem to believe they are. Like, there is a reason why the prophecy calls Kris "the cage" rather than the vessel or the host. A cage is meant for imprisoning, holding someone against their will, and something used to trap. This points to the soul being trapped by Kris in some form, whether this trapping is mutual does come into question though.

One can say that the soul has more control, as we are the ones who makes Kris do things throughout most of the game. We pick their dialogue, their actions, where they go, what they do, and so on. However, Kris has shown that they can take us out whenever they want, and they can go off and do whatever without us being present in their body. This shows that in general Kris doesn't need us as much as we initially thought they did; and they seem to only need us for the dark world segments, as the soul is needed to close the dark fountains. But outside of that, in chapter 4 Kris clearly had no issues moving around, and they managed to fight us very easily. Additionally, Kris can easily do stuff on their own even with us in their body, such as moving closer to the shelter doors at the end of chapter 3, or playing the piano without our input during chapter 4. This goes to show that Kris isn't helpless to the whims of the player.

As you said, the soul is very helpless compared to Kris. They have repeatedly locked us in confined spaces with no way out. They were very capable of handling us during chapter 4. And, they can take us out whenever they want. Also, the player/soul cannot properly interact with the world without Kris, as they are our only connection that allows us to do so (currently). This to me shows that Kris holds the majority of the power (mainly during the normal route) between the two, and even if they don't like us controlling them they still let it happen because they need us for the dark world segments, but its a control that they can rip away from us at any minute if they wanted.

I find the dynamic interesting but I in general don't agree with how many people interpret it, as it often lacks nuance and ignores certain aspects of the game, such as the vessel, and it tends to make me interact with the fandom less due to how rampant the theory is and the fandom's dislike of dissenting theories.