Best Camera for Jewelry Photography?

[JewelryPhoto]

Currently shooting with a 6D Mark II & 100mm EF lens.
Looking to upgrade the camera body but keep the lens.
Cost is not an constrain, but if spending more I want to make sure I'm getting a noticeably better result or at least saving time.

Specific uses:
1) Jewelry photos. Using a light tent and 2 strobes. And image stacking with external software.
2) Just started taking jewelry videos on a turntable. Using a light tent and constant LED lighting.

The main reason for the upgrade is the 6D cant do 4K video. 1080 is not high enough, But I'd also love an improvement in my still photos.

Cameras I'm considering: R5, R6, R7, & R8

I guess the easy choice is to just buy the R5 and be done. But if a lesser camera will get the same results for my use, why pay more?
If you were me, which would you buy and why?