You can technically do malacha up until shkia but the custom is to stop all melacha at candle lighting 10, 18 or 40 minutes prior to shkia ( sephardic, ashkinaz or Jerusalem customs) . Among sephardim it is not assumed that you accepted shabbat upon yourself at candle lighting, but most people stop melacha at that point anyways. Among ashkenazim it is assumed that you accepted shabbat upon yourself at candle lighting unless you consciously had in mind not to, in which case you could do malacha until shkia but it's not recommended and should probably be done only in case of great need.
To the best of my knowledge there is no further universal halacha in regards to a prohibition on "work-work", i.e. your official job whether it be at a place of work or at home, beyond the above.
The article you quote says there is an opinion in the Shulchan Aruch that one who works after the 6 1/2th hour of the day sees no bracha from this work, but then goes on to say quite explicitly:
There is no issur involved when one works later than he is supposed to
on Erev Shabbos.