In case you missed it my comments re the 2s were intended as a joke. I could have dropped down shutter speed considerably and thus ISO if my subject had just stopped moving.
I know, I thought I was joining in on the joke but obviously my humour was off the mark data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
It's likely too subtle for me. Rather than your punchline of "For my upcoming trip to Cuba I'm taking a 200-800mm eq lens",I would have gone myself for the old Mae West standby: Is that a Panasonic 100-400mm lens in your pocket, or are you just glad to see me?...data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
A fair indication of where my sense of humour is at...data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
Slightly late to the party, but some thoughts in case they help...
It partly depends on budget and what you want to shoot. For hand-held video the more stabilisation, the better AF and the better sound the happier you'll be. You can cheat AF a bit by having a lot of stuff in focus (meaning a wide-angle lens).
Remember you can get smaller FF mirrorless cameras but the lenses are still quite big and heavy generally.
I think the Camera options are probably:
Sony A7III
Canon R
Fuji XT3 or XT30 (I know not FF but not bad compared to the 5D3)
Nikon Z6
Sizes:
Compact Camera Meter
Low-light performance (move box around in top image, change ISO in top left sub-image to change all):
Studio shot comparison: Digital Photography Review
Lenses:
The problems here is the 24-105 lenses you probably want are quite big and may not even exist in the system. Plus while you can adapt your 24-105 seamlessly to the R it gets even bigger. Also using the Sigma MC11 (you want that, not the metabones) to an A7III isn't great for what AF features you get:
Compact Camera Meter
The Sony and the Nikon have in-body stabilisation (IBIS ), which is better for video, especially with a stabilised lens.
The Fuji lens you probably want (the 16-80) isn't quite here yet, so it's wider/faster/heavier (16-55), not-so-wide and lighter (18-55) or more super-zoom-ey but less quality (18-135). The IBIS camera isn't as good as the two I list, so it's stabilised lenses for video.
The R has a crop in 4k video mode, but you can use a EFS 10-18 to help with that.
I'll stop there in case you've already decided, feel free to ask questions if not and anything here is of interest...