As for the differences between Convivial Solipsism and Many Worlds, I am indifferent to them. It is immaterial to me whether I am a singular observer who can only be aware of part of the wave function, or I am one component of a superposition of observers, each of which is only aware of part of the wave function.
I personally lean away from solipsism because I do not think that I, or my observation of reality, are that important. But that is a preference. And I don't have any particular justification for it or reason to disagree with anyone with the opposite opinion.
A.k.a. Wigner's Friend.
https://en.wikipedia.org/wiki/Wigner%27s_friend
> QM describes the cat leads to MW being true for the cat no matter what is ultimately true.
You should read this:
https://www.nature.com/articles/s41467-018-05739-8
And this:
https://arxiv.org/abs/1812.06451v4