I also can't run PW on fullscreen on Windows 10, as it just leaves me with a black screen.
changing the size of the client actually works its in Game Functions and a drop down arrow with numbers like 1738 x 679 etc etc changing that should change your skill bar and the other things sizes P.S you need an extra genie skill lol
PW isn't optimized for anything higher than 1080p. On windows you can turn on scaling but that will make the rest of your os look like shit
I can't help you with anything but this; I can't run it in fullscreen on Windows 10 either, but a friend of mine gave me a little tip the other day to make it almost like Win 10. Go here: System settings and change this To your resolution. (Mine is 2560x1080, so I took down my width so I could have it borderless+full screen but I got to keep my taskbar like this
On windows you can turn on scaling but that will make the rest of your os look like shit