😄 It's quite alright. I definitely understand there's a lot of things to consider. The articles I write take upwards of 40 hours each just because of all the research and details that go into them. I often get overwhelmed with all the information that goes into these decisions.
It is helpful for me to put everything into smaller categories so I can tackle one at a time instead of trying to think of everything all at once. It appears you've nailed down that you will be using two of the BMPCC 4Ks, so I would consider that as one check mark down.
Next, I would nail down the switcher. That will determine how much budget you have left for lenses and camera support. For instance, the SlingStudio plus 2 of the CameraLinks will cost considerably more than an ATEM Mini Pro (or even the ATEM Mini Pro Extreme).
One important thing to keep in mind is that you will get native remote control of camera settings like aperture, white balance, record start/stop, tally, and possibly zoom and focus (depending on the lenses you get) if you use the BMPCCs and any of the ATEM Mini switchers. You will not get that functionality with the SlingStudio at all.
So, if you're cool with this approach, let's start at the switcher and work our way to lenses and support after that.