Spectacle is a free Mac App that I use constantly throughout the day. It allows you to easily organise your windows without using a mouse.
You can easily jump between 1/3, 1/2 or 2/3 window display on your monitor. I customarily use 4 windows spread over 2 monitors, so I have Spectacle divide each of my monitors into 2 windows.
To make things even easier, I use the preferences customisation in Spectacle to assign the right & left window options to function keys. Click on the window, then hit the right or left assigned function key. Hitting them multiple times scrolls through the 1/3, 1/2 & 2/3 options. It’s a very powerful utility that becomes second nature after a while.