From amfetamine to MDMA; oxygen, furan and the extra methyl group

[Sublimo]

I had very good experience today with 6-APB. The chemical structure of it started a thought process that I would like to share with you. I know what amphetamine feels like, neat, streamlined and clear. I know how MDMA feels, warm, fuzzy and anything but clear. 6-APB has the same warmth as MDMA but it has the clarity of amphetamine. After some research I found a couple of structures that only differ in the amount of oxygens in the furan like structure, the position of the oxygen atom and the presence or absence of a methyl group on the amine. The chemist in me gets very excited about this. Is it the extra methyl group that makes it fuzzy? Or is it the extra oxygen atom? And what about the position? Is there a difference? I'd would like to think so.

I would like to try to map with experience of you what these compounds feel like and see if there is a certain pattern. To enlighten the question I draw a beautiful scheme.