After much time wasted with struggling to get VNC working on Ubuntu that stands for without monitor box - I've compiled the below draft notes on how I finally managed to configure the damn VNC. This should be stated, that I've come a long journey from systemd/init.d configuration scripts, through various VNC daemons (tightvnc, tigervnc, xvnc) and experienced lot of issues (VNC starting before X, VNC not having Xauthority, VNC not being able to open display :0, and so on) .
Finally, this below setup got me working with VNC.