hi,
Both works for me, booting headless or unplug the monitor after you have everything set up.
I find it hard to recommend this board, generally I find it hard to get a consistent behavior out if it. currently I have gigabyte 1037u that is working 24/7 for 5 years no problem, this one I'm still testing.
on J4205 hw transcoding still buffering in Videostation but In Plex seem to work ok . I'm currently checking why transfer rates are inconsistent sometimes.
With all this said if you need hw transcoding or you try to get as close as possible to the real DS918, DS1019, DS619slim, apollo lake boards are your best bet. Maybe Gigabyte has a better implementation with GA-J3455N-D3H if you can find one.