I am a bit confused about per-monitor dpi-aware in WPF. I thought you need to do some work to make your windows scale properly on different monitors (as described in Developing
What you see is an example of System scaling when one app window moves to a different monitor with a different DPI. That is because WPF apps are by-default System DPI Aware. As a result, if you notice carefully, you'll see WPF visuals/text gets blurred when the target DPI is higher or they look fuzzy when the target DPI is lower. Also, note that monitor resolution does not matter for WPF apps, since WPF is device resolution agnostic (it's measurement unit is Device independent Pixels).
Good news : .NET 4.6.2 preview just got released and it hasPer Monitor DPI Awareness out of the box. Check out the developer guide and samples here :
https://github.com/Microsoft/WPF-Samples/tree/master/PerMonitorDPI