Scenario (based on Ashkenazi practice):
An Israeli Cohen who is visiting in Diaspora is there on either Shabbat 8th day of Pesach or Shabbat 2nd Day Shavu'ot. For him, it is a "regular" Shabbat. He is attending a Diaspora shul where they duchan.
I know that in Israel, they duchan daily, so, this wouldn't be any different for him. However, does that factor override a general rule of observing minhag hamakom? In other words, in Diaspora, Birkat Cohanim is done only on Yom Tov.
So, is there any type of conflict, here? On the one hand, it is not a Yom Tov for him, and privately, he is praying only the Shabbat prayers. So, should he act as if he were observing a regular Shabbat being in Diaspora where there wouldn't be Birkat Cohanim on Shabbat? Or, should he act according to the what the shul does, and it being Yom Tov, he duchens with the rest of them? Or, does it not matter at all b/c he duchens daily, anyway?