SBonnevie

I'm running Cura on a setup with three monitors: my laptop monitor, which has 100% scaling, and two auxiliary monitors, which have 150% scaling. I had a problem where Cura 5.1.0 (not 5.0, curiously) would open with 100% scaling even if it was on one of the auxiliary monitors. Don't worry, I'm not going to tell you I updated my drivers like 90% of others (although it might be worth checking to make sure they're up to date anyway). I fixed this issue thusly:
Pull up Cura 5.1.0 on the Start menu Right click on it and choose Open File Location Right click on the shortcut and choose Properties Click on the Compatibility tab Click Change high DPI settings Click Override high DPI scaling behavior and choose System (Enhanced) from the drop down.  
If this doesn't solve your issues, try this thread and the threads linked within it for other fixes: https://github.com/Ultimaker/Cura/issues/8966