Only caveat is I've always completely used matrix off in custom mode, and shot Slog3 gamma 99% of the time, with only a couple of HGs when the footage was handing off to non-LUT familiar editors for safety.
Looking to test Cine EI more thoroughly when I have some free time in Feb, I've just been too back-to-back with quick-turnaround jobs when I couldn't afford to need in-cam NR and have to deal with/explain the change of modes mid-shoot. I shoot mainly obs doc.
I am a dissenter from the view that Cine EI is always better than Custom. Most of my clients want WYSWYG video. While I often shoot Slog with a LUT burned in , even more often I actually find it too flat for the snap my clients want. Contrary to a lot of what you hear on this forum I find the flesh tones of Custom perfectly good for many uses, and apparently so do my clients. It all depends on the shot and the situation. I'm non partisan.
I personally think Davinci Resolve is going to replace Premiere in the next years, as adobe indesign did with the former market leader Quark express. And if that happens I think the preference of the clients for ungraded material will grow. But that is just my theory.
At the other hand, perfect material ready to use and broadcast, right out of the camera is always the best.
I is good the camera can do both.