The point is that I'm not happy to do this directly, for various reasons. I don't want to open up any ports that get forwarded to my LAN for remote desktop, and I want to be able to access LAN clients from machines behind a proxy that just blocks anything but http/https traffic. That's why I looked into Guacamole.
Maybe RDP connections work better with guacamole, compared to VNC, but I don't have any windows machines I want to remote into, so that's of no value to me.