Ive edited in FCP, FCPX, and Premiere for years. in the end I prefer Premiere. Although I like the simplicity of FCPX.
You're comparing the BMPCC and the GH5S to the Sony A7SII? The A7SII is not even in that same ballpark of cameras and I still have my reasons to buy the Sony A7SII than the BMPCC.
I can easily color match canon footage to match sony footage. To me color science doesn't matter if you know how to grade footage.
or you can make it into an external GPU