This is pretty late but I wanna reply as a shia inclined Quranist myself.
Basically first off welcome

and how I see things as a shia inclined Quranist is that:
-Considering the religion was new and considering the fact that God had promised to keep this book and religion perfect, it would only make sense for God to send people who would keep according to the Quran.
-During that era you had the Caliphs coming in such as Abu Bakr and Omar and especially Yazid who wanted to change rules that were allowed or disallowed in the Quran. Thus the belief is that you have the imams who opposed change.
-the imams i've realized reference the Quran and not hadiths like what Omar tried to do at times (probably a bunch being fabricated) thus they were great Quranists themselves.
-While there are hadiths from both Muhammad and the imams in traditional Shia Islam, the only hadiths I might look for are ones that back up some claims in the Quran and reject all those that contradict or add new rules to the Quran.
Thus Shia Inclined Quranism