MDAI... somehow this thread always seems to come up with old RCs over actually new(er) ones. this one has been around for at least 3 years. personally ive found that it can vary a bit from vendor to vendor, batch to batch, with no relation whatsoever to the actual color (ive has awesome white and tan and brown and whatnot). however, i wouldnt go so far as to call it mdma lite... its not on the same level of entactogenicity, no push... just mellow happy times, that do go well with a bit of booze.
in combos it is far better, but ive found that whenever i comboed stims or other entactogens with it, it also increased the resulting comedown....
with 2FA, there are few reports because for some reason people dont post in the big and dandy thread on it!

doses for 2FA for me range from 30 to 60, anything more doesnt add anything really. the duration is a nice short simple 4hish, with little to now comedown, but also little to no fun. its what i would use instead of coffee.
2fma is a smooth, calm streight talking stimulant, with a bit of a fun side if mixed with alcohol, with little or no serotoninergic or entactogenic ability, doeses are from 50mg upwards, depending on what the ROA is and desired effect. duration is somewhere in the 6h+ depending on dose and redoses of course. it too has a ceiling effect at some point, but not as low as 2fa's. careful with high doses is sex is wanted, as it might impede the boys... little comedown.
4fa is the party animal of the FA family. it is my go to for fun nights out that will most likely include sex. serotonergic, can go quite high with the dose before becoming tweaky (i dose round 120mg but im quite sensitive to stims). comedowns are bareable, provided no redoses and plenty of water vitamins and food on the way down
4fma ive only heard bad things about, so much so that i havent tried it yet.
the 3fa i have ive never tasted. apparently its a bit neurotoxic or something similar, but is apparently closer to 4fa than anything else.
serotoni sounds awful. the 4MAR analogues sound fishy to me. as of yet ive not heard reliable reports of their use