CS:GO is better played at 1024p stretched for visibility. If I alt+tab out of the game, the resolution is changed back to 1080p until I go back in the game, this creates a lot of lag. So I change my resolution before I start the game to avoid lag or window reordering.
I use set-screenresolution to quicky change between resolutions instead of opening my graphics card app and changing it there. This is a lot more conventient if you're playing on and off during the day.
I placed two scripts on my desktop to switch between resolutions when I'm playing, this helps a lot.
setres.ps1 and replace the resolution line to your desired resolution, then run the script by double clicking or right click + run.
Can't run the script? Open Powershell as admin and type this