SSHive's VNC viewer opens a remote desktop in a tab of the same Mac window as your SSH sessions. It connects straight to the VNC server's port, 5900 unless you changed it, with nothing to install on the server beyond the VNC server itself. The picture fits the window or shows at actual size, a View only switch keeps stray clicks off the remote desktop, and text copied there lands on your Mac's clipboard. VNC is a Pro feature.
Whether a server lets you in depends on its authentication type, so here is the full list the Mac app completes: VNC password, RSA-AES (RealVNC Server, since SSHive 2.0.4 for Mac), VeNCrypt / X.509 (what wayvnc uses, since 2.0.5) and Apple Screen Sharing, to reach another Mac. A server that only offers something else refuses the handshake. On iPhone and iPad, the
VNC client for iOS uses a different engine: it adds UltraVNC MS-Logon II but has no VeNCrypt, so a wayvnc host that requires it is reachable from the Mac only.
A VNC server does not belong on the internet. The usual route is an SSH tunnel: forward local port 15900 to port 5900 on the server and point the VNC profile at localhost:15900. The port is 15900 rather than 5900 because a Mac with Screen Sharing turned on already listens on 5900; the
VNC guide for Mac shows the tunnel step.