I asked my Rav a question concerning wherever I should listen to the Rashba or the Sages of Provence, on wherever it is ok to learn philosopy to study Masseh Merkava and/or Masseh Berishis, before you are 25 (mentioned in Artscroll notes on Talmud Chaggiga).
My Rav answerd you have to listen to the MODERN POSKIM (not the Rashba)–wherever he meant this just for this question or in other cases as well I am not sure. Though he did speak in a shiur he once gave that people should not listen to a Rov from the past, over a living posek today (wherever he meant this a halacha or maybe it was a Aggadata or Derush like a Brisker vort that or Rogatchover that is not followed always when it conflicts with Halacha).