My guess
Interestingly the one I was most confident about is the third one being the path tracer. Lumen has very noticeable over-occlusion in the corners of rooms where walls (and other meshes) meet, and produces a warmer color temperature than the path tracer.
Until the OP mentioned that they placed no reflection captures and were not using raytraced reflections, I wasn’t sure the first was lightmass. Especially since GPU lightmass can match the pathtracer quite closely, potentially closer than Lumen if used with raytraced reflections.