Joseph, See the first tosfos in shas, i.e. Brochos 2a, where Rabeinu Tam holds that you may be yoitze shema (probably lechatchila) from whenever the earliest time for davening maariv is. We don’t pasken like that lemaase, but it certainly seems that R”T’s hakpodo was more on Melochos after Shabbos/Yomtov than everyday maariv.
YY, It’s interesting that you mention Friday, as I asked Dayan AD Dunner of London if Friday is different. He explained to me that there are two reasons that it is different; in halachic terminology, why some are meikil on tarti d’sasri on Friday. Firstly, maariv on Friday creates its own time zone called Shabbos. So, there is no tarti d’sasri. And secondly, Maariv, is k’neged the haktoras eimurim, which was not done on Friday night. Nevertheless, more ‘Yeshivish’ communities are generally machmir to have mincha before plag/shkia and maariv afterwards.