What resolution is your screen? - the windows have to be a certain power of 2, as we learned when 1366 wide screens came out for cheap laptops (like my Dell one). I think they had also to be a multiple of 4 pixels, too.
One thing that will affect that is
the size of the borders your desktop "theme" uses, so it is worth experimenting a bit to see if some scheme gives you thinner window margins. (The one I use in windows 8 is a bit "fat", and so leaves a 2 pixel unused zone. It also has a large title bar.)
Scrolling - experiment with the scroll width setting in yhe game options launcher programme misc screen. You need to have one large enough to allow for the task bar, but not so wide that hovering over the right hand edge of the right roe of buttons will trigger scrolling. I use a scroll sensitivity size of 25 pixels, scroll speed 30, on my 1920x1080 monitor.
Also, train yourself to hover the mouse
just inside the window edge to trigger mouse scrolling, rather than just "ramming it to the edge" as with full screen mode. I trained myself to do that several years ago, and it was not too hard to get used to
!