I find the best method to create dynamic apps that resize depending on people's window size is going with a 16:9 ratio and Scale to fit and Lock Aspect Ratio both turned off.
The next step becomes making extensive use of the App.ActiveScreen.Width, App.ActiveScreen.Height, and App.ActiveScreen.Size properties for positioning, control sizing, font sizes, etc. This is also a good opportunity to learn and practice using Horizontal and Vertical Containers. They take some initial set-up, but it is amazing having a whole set of controls able to wrap around underneath another container.
As an example, this settings screen in one of my apps has a bunch of nested containers. Horizontal container containing two vertical containers, then additional containers within. The whole thing wraps down to one column when the window is made small.
