Are you using the built-in macOS client? macOS screen sharing has some VNC extensions that make it usable on both wireless and WAN networks. I've been VNC'ing to my 2560x1080 work machine from home for years through a layer 2 UDP OpenVPN tunnel over WAN to great effect (connect to OpenVPN, cmd+K in Finder then vnc://10.20.30.40/). Using the now defunct Back to my Mac always was a crapshoot though (probably due to lack of port opening, therefore an intermediary has to be used)