A number of PEA's and tryptamines that are commonly referred to as RC's actually do have some significant research behind them, though nothing near the biggies like LSD, MDMA etc. AMT and AET were explored in pharmaceutical R&D as antidepressants, and 2C-D was explored extensively by Leuner in psychiatric research, as were 4-HO-DET and its phosphate. It appears that Leuner and colleagues ran some neurotoxicology studies in addition to studying subjective effects. This research is hard to find in the published English literature, though.
2C-B is a good example of a chemical that's in the borderland between "mainsteam, tested drug" and (so-called) "research chemical". There have been a few studies and quite a number of anecdotal reports. We don't know how safe 2C-B really is, but we do know that no one dies from taking an average dose. We also see few if any accounts of long-term users developing problems, though there have been no longitudinal studies. As the saying goes, absence of evidence is not evidence of absence. Actually, I do know of an individual who twice developed worrisome signs of dopamine depletion after taking a single dose of 2C-I and 2C-D; this went away after a few weeks, but still. (
Link .)
But yeah, we really don't know the long-term effects of most so-called RC's, and we can't assume that minor changes in the molecule won't affect toxicity. Obviously minor changes can dramatically affect activity, e.g. adding two little methyls to a tryptamine's N-substituents: 5-MeO-DMT --> 5-MeO-DET or 5-MeO-MiPT. If activity can be so strongly changed by a little tweaking, such that a compound goes from being orally inactive to orally active, then its toxicity can certainly change too. An even better example is DPT --> DiPT, where the number of carbons stays the same but the points of attachment to the N are just rearranged a little.
It's probably smartest, if one is going to use psychedelics, to stay with time-tested one like shrooms, LSD and cacti. Personally, I think that 4-HO-MiPT is probably just as safe as 4-HO-DiPT, which is probably just as safe as 4-HO-DET, which is probably just as safe as psiilocin. I say that because, apart from some variation in potency, there isn't much subjective evidence of the compounds acting differently. But that's just a moderately educated guess.