any way to use this for e.g. vnc forwarding directly? I mean, I can set it to be available via ssh but would that work?

ssh [email protected] -N -R some-pc:5901:localhost:5901

Now do I reach this from my vnc? I need the "someuser" and -J part when connecting? Would I have to setup another ssh connection from my local pc to ssh-j and then use localhost:5901 in vnc?