Hi Brian,
You should be able to play both games on a Windows 10 machine. I have no direct knowledge of Windows 10 I'm afraid, I chose to stick with Windows 7 which allows me to play all three Ship Simulator games with no problems.
If you bought New Horizons as a download from Vstep you can re-download again with no problem I feel sure. Possibly best to unregister it from your profile though, and then re-register on your new machine.
I apologise for the delay in responding to you request, and ask your forgiveness.
Angus.