OPi Zero H3 - overscan issues?

Hi all,

Today I decided to pull my OPi Zero H3 out of its box and fire it up. Downloaded and installed Armbian Stretch mainline kernel 4.14.y to a SanDisk micro sdcard grade 10 and powered it up with a known good 5v 3a power supply I've used to power my OPi Zero's via GPIO (with all my Zero's I've soldered in GPIO headers - something I'm used to doing with RC helicopter and multirotor flight controllers).

Connected my USB hub with keyboard and mouse connected. Disconnected my OPi One (RetrOrangePi gaming computer) from its HDMI connection and connected it to my Zero H3 and powered it up.

Boot text is on display nice and clear. Then the desktop starts - with terrible overscan / flickering / multiple screens trying to be displayed.

Is that fixable via editing a configuration file? My skills with Xwindows or window managers are extremely limited as I usually just use SSH (with the exception to RetrOrangePi where I just use the supplied and working graphical interface).

On the TV I'm using HDMI input. I cycled between its display settings from Auto, 16:9, 4:3, Full screen and Dot-to-Dot (I had to use Dot-to-Dot for RetrOrangePi to display properly).

Secondary question - is the wifi on the Zero H3 the same as the Zero - as in completely useless? My thought is if I can't get it to display properly I may use it as an Octoprint server.

Thank you to the Devs for production of Armbian!

TIA