I have a Dell XPS15 9550 with dual graphics.
Installed 381 nvidia drivers with prime and using Intel graphics mainly from nvidia-settings.

Trying to scale display from Settings but don't see any changes on decimal values, i.e. 1.4, 1.6, 1.8, etc. 1.5 seems to be working but is a bit unstable (some things get duplicated,, etc.). The best option so far is 2, however I'd like to make things a bit smaller.

Also when changing onto a value with decimal point graphics get very distorted after a few minutes of use. Like the animation of minimize/maximize looks broken.

Is this a drivers issue or something with plasma?

Plasma ver is 5.8.7 on Linux Mint 18.1