Hey Kortan,
With the screen flickering the first thing to check is make sure your graphics card(s) drivers are fully updated. If they are and it is still flickering let’ s first reset your in-game settings. To do this go to your Documents folder and to the StarCraft 2 folder. You will delete the variables file there, alternately you can delete the entire SC2 folder however, it does contain replays and such in the Accounts folder. So if you delete the full folder I would recommend at least saving that folder.
Let’s also run the game in windowed mode.
Click the Blizzard icon on the Blizzard desktop app.
Select Settings from the dropdown menu.
Click Game Settings and check the Additional command line arguments box under StarCraft® II.
Type -Displaymode 0 in the box and click Done.