A buddy is thinking of jumping to PC. And he is looking at one of these with Intel Core i7-8700T. (That is a low power version). 16 GB of RAM.

It is one of those PCs built in the screen.

Reason I ask is that I always build myself. It is ste same CPU as I got in mine, but i have the "K" version.

The all in ones are basically a modified laptop motherboard with a desktop display.  Usually no room for adding additional drives, ports, etc.  
It looks like a nice all in one, but I personally would not buy or recommend them for DAW use.
 
 

It may be the same CPU (even if were the K version), but it won't be able to run at the same speed as in a tower.
 
The cooling apparatus in tight enclosures is a compromise (compared to the cooler you could use in a tower).
 
ie:  If you were running an 8700k in a tower, you could lock all six cores at 4700MHz.
You can't do that with the 8700 (non K version).  Even with the 8700k... in that all-in-one enclosure, the cooling isn't adequate to run all six cores at 4700MHz.  The CPU's performance is throttled to keep temps down.