Hi ,I am going to upgrade my monitors to 4K, What`s the best Pen display to use with blender?
Welcome 
…
Anything mentioned on any test like so:
or recommended by artist:
depends also largely if you want to draw or sculpt with this… the phusical size which fits in you place and last but not least: your budget.
and maybe your OS… 
(The performance of your system is also a factor when doing high details.)