We observed both cooperative and nucleation and growth behavior within the 2DQTT-o-B system, allowing for direct comparison of molecular origins of these transitions in a single material. We discovered the I-II transition exhibited cooperative behavior, resulting in a rapid, shape changing transition dominated by avalanches as defects were introduced. The transition was found to be driven by changes in the alkyl side chain confirmation, as revealed by Raman spectroscopy. This was in striking contrast with the slow, smooth II-III transition showing clear nucleation and growth behaviors. Unlike the I-II transition, the II-III transition was driven by changes in spin-spin interactions through biradical formation which is the observation of biradical interactions triggering a polymorphic phase transition.