Why did I not do a better search months ago? As the SuperUser.Com post states the answer is to change the compatibility settings for the manager by right clicking on the file 'C:Program Files (x86)MicrosoftRemote Desktop Connection ManagerRDCMan.exe', selecting compatibility, change high DPI settings, and unchecking high DPI setting override Once this was done, I have readable resolutions on all screens. This is bad whether working on the single high DPI laptop screen work with an external screen. I either get huge fonts or microscopic ones. However, if I use my preferred tool Remote Desktop Manager 2.7 (as it allow me to store all my commonly used RDP settings) I am in DPI hell. If I use Remote Desktop (MSTSC) as built into Windows 10, I can drag sessions between the two monitors and the DPI shift is handled OK. This is one of those post I do mostly for myself so I don’t forget how I did something, it is all based on answers on SuperUser.Com, I can claim no credit I have a SurfaceBook (first generation) and when I am in the office it is linked to an external monitor, with a different lower DPI, via a dock. mRemoteNG also has the advantage that it support most major remoting technologies not just RDP, so I am giving that a try for a while.

Updated 3 July 2018 - A colleague, Andy Davidson, suggested mRemoteNG as an alternative tool to this address this issue.

Remote desktop manager windows 8