Wanted to chime in on what I've used so far (and I have a few relatives that are kind of tablet-crazy that I can ask to try out).
Also I'm using this to hold them (Been using it for even the phone as I like the way it's secured)
https://www.amazon.com/gp/product/B095Y9F751/ also not using any kind of hood/shade which I should probably look into.
Samsung Galaxy Tab A7 10.4" (2019 I think), flashed with Lineage 19.1 (Android 12)
It's barely bright enough to see out in the full sun yesterday, but did ok with a little shade despite a little bit of screen glare, it feels a little underpowered with some of the apps. I had it connected to my phone via a wifi hotspot to be able to get things like authorization/mapping/etc. DJI flew and worked, and could do a panoramic, but there was some slight delay in accessing functions/menu. Litchi at one point froze for a few seconds and could not get the app closed to reopen (I can probably fault this more on a custom rom than the tablet, and will retest after I flash back the official samsung image). The 10.4" size seems to be that ideal middle ground, large but not too large, and the tablet itself is reasonably light/thin, but feels a little underpowered even if it meets the 3GB ram minimum.
Samsung Galaxy Tab S7+ (128GB model with 6GB ram) 12.4" (latest official stock rom)
Definitely a large screen and had no problem with responsiveness, bordered on being a bit heavy to use, but thinness was not an issue. However in my brief usage of it found it to be not quite as bright to be usable in direct sunlight.
Compared to both of those, a Samsung S22 phone was much brighter (Brighter than my A71 which is brighter than both tablets at max), much more responsive without any glitching in either app.
Had I known about Tripletek before I got the S7+ I would have probably gone that route purely on brightness, but at the time I got the S7+ I was using a little DJI Mini and wasn't thinking about going overkill on a tablet setup (I didn't get the S7+ for the purpose of the drone).
TLDR : Tab A7 (10.4" 2019, 3GB Ram) is usable on a lower price point, and can be flashed with a leaner custom rom, but may be a little under powered if you're switching apps. A7+ (12.4" 128GB/6GB) definitely large and powerful enough, but lacks brightness in sun. The S22 (8GB ram) and A71 (6GB ram) phones do better on brightness than the either two tabs, the S22 performs software wise better than all of the above, the A71 did better performance wise than the A7 tablet.