Without setting any priority research, the mod seems to favor the tier 2 180 degree inserter research which requires both red and green science packs. However, there are still two dozen researches available that only take red science packs.

I think the reason is because the time component for that research is 5 seconds, where the time requirement for other researches is 10+. Would it be possible for the third criteria to check the types of science required or to pick the top-left most research option?

Heya. This sounds very much like a feature I had to remove some versions ago. The problem is that other mods (such as Bob's Modules) add new research ingredients, and AR can't really know that one research ingredient is more difficult to produce than another (technically it's possible, but the shots I had at it were all inferior to the current filtering system). This lead to AR researching Bob's Modules stuff early on, because they required few research ingredients and had a short research time, but the player still were nowhere near automating production of those research ingredients.
This is why I replaced it with a filter system instead. If you want it to fully research red science before moving on to other science packs, then toggle off the other science packs in the GUI. This is also quite useful later on when you've automated some of the science packs, but not all (and don't want those to stop research).