Peacock is my biggest frustration. A lot of 24fps content, and the judder is noticable. I end up manually changing frame rate and then needing to change it back. Their support is unfortunately worhtless when trying to request for a fix for this.
For HDR, yes, enable manually as needed and then change back. I think Fox Sports pulled HDR support entirely from Apple TV several months ago for some reason (4K content is listed as "UHD" instead of "HDR" as it is on Roku), and it does seem to support frame rate matching.
I wish the app makers would just use the standard Apple API. The apps you listed are the ones that have non-standard UI that means not all standard features are fully implemented. I'm actually surprised Apple allows this.
One more for the list: Prime. Supposedly TNF games are in 4K HDR, but it's definitely not switching.
It's a good time to find out! Apple's holiday return policy is in effect. You can return up until January 8 if you don't like it (https://www.apple.com/shop/help/returns_refund).