If you do look back into it:
The Studio 2s have much more impressive specs, same as the laptop I just recently retired, that are more on par with CAD requirements but they come with a price.
You may also want to check out Wacom. You can add a digitizer display to an existing setup. They have some smaller screens that are fairly reasonable and they also have the option to upgrade some of the bigger displays with a “brain” and make them a complete computer. I think their attempt to compete with the Surface. I like the fact that they have a 17 key configurable keypad. The keypad seems like it would be perfect for cad shortcuts depending on its capabilities cutting out the need to try and 2 finger keys on opposite ends of the keyboard.
Wacom Cintiq Pro: creative pen display | Wacom
I am looking at the Wacoms because like you mentioned the specs of typical touch screens are not great without sending a fortune and the ones with some power tend not to be portable.
I’ll keep you posted if I pursue anything.
Also, I wouldn’t be opposed to a TBC version for my Hololens.