I use Autohotkey for resizing windows all the time. I have several different hotkeys that will resize to different sizes and positions depending on the window I am moving / resizing.
WinMove A, , 300, 50, 1024, 1001,
will move the active window 300 pixels in from the left and 50 pixels down from the top. It will resize the window to 1024 pixels wide and 1001 pixels high.
The hotkey combination is Windows + 1
I use this particular hotkey to resize my browser.
If the window is already maximised when this hotkey is used, it remains maximised in the new position and size so that clicking on the maximise / restore button in the top right will restore the window to the previous non-maximised size.