Joseph – GRA L’Chumrah or RT L’Chumrah. Either way works. I’ll even agree with you that many Yidden will hold RT as primary and GRA L’Chumrah as secondary, but I don’t think (and correct me if I’m wrong) there is any real difference.
Regarding the (but not all): Are you aware of anyone who will (for example) do Milah on Shabbos for a baby born 55 minutes after early shkiyah Saturday, which is 3.5 minutes before RT Shiyah (pashtus), and after Rav Moshe’s 50 miuntes? Like HaKatan and Zionism = AZ, many will state that they hold certain shittos, but when the chips are down, they hesitate to put those shittos into practice.