Is there something similar to RemoteApp for MacOS
You could say that the X11 system for macOS supports something similar to RemoteApp - i.e. allows you to run an app on a distant server and it shows up on your desktop like any other app in its own window - without a full desktop environment like VNC.
However you cannot run the Messages app this way.
The only solution I can think of that comes near to what you want is to run macOS in a virtual machine on your Windows computer, and then use features in the virtualisation software to show each guest application in its own host window. In VMWare this is known as &quot;Unity mode&quot;, however VMware currently only supports that mode for Windows guests. In the theoretical case that a later VMware version supports this, remember to check that your for macOS at that time allows you to run the operating system on Windows.