Are you running two different resolutions? One large desktop?
Two different resolutions.
The old monitor is a 1080p. I use it to do all my apps and the like. For example, I'm full screen still on Elite Dangerous Odyssey on the 2k monitor while I type this.
Used to, I've have to alt-tab out and back in and all that jazz.
The really cool part is being able to leave my Elite Observatory and EDDiscovery windows open on the 1080 monitor and see it at a glance rather than having to alt tab all the time to see them.
Hopefully, there will come a day where I'll have 3 4K monitors for a surround view and a 5th for my apps and web surfing.