In my experience with them, MSI laptops tend to run quite hot in general, your OS probably isn't going to fix it. You can try one of those laptop cooling plates, basically a mesh platform with fans, ensuring cool air is always available to the laptop intakes, but it isn't exactly a perfect solution.
Really it just needs more cooling capacity - they seem to cut razor close to the amount needed in their designs so when eventually cooling becomes less efficient either through fans getting tired/clogged or thermal paste/pads breaking down, it will not keep up.
My biggest hurdle is honestly that GrapheneOS only supports Pixel phones... I had one once and hated it and honestly don't know how much of that was because of google's android or the phone itself and am reluctant to buy a new pixel phone to try GrapheneOS and find out I still hate the hardware. I've had a much better "out of the box" experience with Samsung phones (and love that my current one has an sd card slot and headphone jack - but I know that's pretty much non-existent on new phones) but am finding they are so locked down and closed off by Samsung you can't really put anything else on it and have it work properly as far as I can tell.
It's time for a new phone, and I'm honestly not sure what to do... The easy route seems like getting a pixel and putting GrapheneOS on it before doing anything else, but I just don't super trust that the hardware isn't going to drive me nuts...