Is the Canon R a good fit for me?

Hi. Long-time lurker and first-time poster.

I currently have a 5D (the original one), with I think 6 Canon lenses, 580EX and a bunch of accessories. My lenses are generally the mid-range L ones (F4 zooms and the like) rather than the super expensive ones. I do really like the lenses even if they're getting a little old now. I still remember my switch going from EF-S to the Ls, where there was a hard to describe warmth I liked with the new glass. I'm looking to make the jump to a new body, and like the idea of a mirrorless (the WYSIWYG aspect) and I do like new tech.

I was quite excited by the A7III earlier in the year, and went to a shop to find out more. A few things put me off though. My hands aren't small and I found it a bit uncomfortable to hold the A7RIII - in fact with some lenses my fingertips would be pinched between the lens and the grip. I asked one of the sales guys to show me the eye-AF and it took him at least a few minutes, including calling over a colleague to get it turned on. Quite impressive feature when he did though, though portraits aren't my mainstay. This was in a well-known camera-only UK store too. He even gave it a shake at one point, and I could hear something clunking around inside - maybe the sensor moving against its stops.

Another thing to give me pause was the many reviews about adaptors which didn't seem to agree on anything. Some said metabones ruled, some said sigma and some said it depended on the lens. The reviews even contradicted each other with their conclusions for the same lens. I really don't want to sell my glass, at least immediately.

I have a Sony RX100V, so I'm used to the menus, though that camera disappointed me by only being able to record 4k for 2 minutes before thermal cut-out - I found this out while surrounded by sharks 20m under the water. I don’t believe the A7III has this problem but it eroded my trust in Sony that they were happy to put out a feature they must know didn't really work.

I'm just an amateur photographer who dabbles in a bit of everything, and like to try new things. I do a little bit of urban, landscape, occasionally 'portraiture' but never posed, underwater (but I won't use the new camera for that - housings are astronomical), nature macro, painting with light and a little makeshift indoor studio stuff. I also occasionally do a little video of internal company presentations.

I'm more of a wait-for-my-moment-and-take-the-shot shooter - I don't really understand the need to have 5+ FPS except for sports. Perhaps the new normal is to bang away dozens of shots and hope you get some good ones.

Does the R seem like a good match for me and will I be impressed coming from the original 5D? Or was I wrong to overlook the A7 with adapted glass? Every new Canon camera seems to be savaged by the internet for one reason or other. I see a lot of talk about IBIS, FF 4k, dual slots and eye-AF but I'm still happy with the photos coming out of my 5D and it doesn't have any of these things. I might miss a few shots but it's not the end of the world.

Apologies for the long post. Thanks