the only pea i have experience with is mescaline, other than a couple of times which 'mescaline capsules' purchased at a festival definitely were a RC of some sort. speculatively 2c-i from everything i read about it, but i'm not going to specifically address those few experiences for my comparison as i can't truly say wtf it was lol.
Ive had breakthrough +3 experiences with mescaline near 30 times i'd say, probably another 20 or so low doses in the +2 range. Definitely have had absolute transcendent experiences with the cactus which are +4 or whatever. feels like this scale is lacking, i feel silly tryping this lol.
No research chem experience, except by accident ^

my tryptamine experiences are limited to mushrooms for the most part, a few dmt experiences.
So, looking through the goggles of my bias binding me through limited (in this case only plant) experience...
it seems that peas are more 'stimulating', definitely felt that with my one random 2c exp as well. but with mescaline, its not so much a jittery stimulation, but rather a seemingly endless 'fuel' and a sense excitement and ready-for-adventureness.
the tryptamines have a definitely 'obe' kind of feeling, and a marked 'lay down and melt' reaction.
tryptamines also seem to involve a sense of movement, in both the visual nature as well as the physical sensations. visually things have a certain 'ticking' or 'flanging', almost 'vibrational' feeling. everything seems to bend or dance in a certain pattern which mesmerizes my focus, kind of snake charmer-esque. some new movement or new dynamic to the pattern is always coming into view in a rather forceful and overwhelming-feeling way. Also these movements and 'ticks of adjustment' which are characteristic visually also correlate to synergistic sensations of feeling. it seems like my sense of physical orientation is always updating, as though i'm falling in different directions (maybe even more than 3d..

) like a sense of gravity pulling me in certain directions...or pulling me into some sort of pulley-operated spiral machine, wherein my sense of 'solidity to self' is distorted or put through a series of multi-dimensional rolling pins until 'i' am a distorted puddle of cosmic goo. even when it's not so physically overwhelming. it always feels like i'm 'traveling' in a turbulent manner, when i go into a trance with tryptamines. a feeling of hyper-drive and and 'other world'liness which is sometimes intimidatingly unrelenting, almost 'too much' feeling or 'i'm gonna go crazy' feeling sometimes lol (when the ego pokes its head in and delusion washes over its eyes that is

)
Mescaline, on the other hand,(and i can see the pea resemblance in my couple 2c exps) has a markedly different character. visually it is not so often ticking movements, but rather spatial and proportional fun house mirror kind of bends. when this becomes turbulent and intense everything can be totally visionary and absolutely as intense and mind blowing as tryptamine visuals, but there seems to be differences. first off, with a high enough dose of mescaline things will be undeniably warped and everything can become 'beings' and full on vionary type images...however, the most intense aspects of mescaline (and maybe this applies to other peas...) come through entering 'trance'. there is a certain 'letting go', which mescaline generally doesn't force upon you (whereas tryptamines generally do), but when one essentially meditates and clears ones thoughts it opens the door for absolutely encompassing visionary states. however, the difference i can note is that mescaline distortions 'stay within the boundaries of the object' in terms of your perceptual recognition of the symbols placement in your perceptual field...though can be completely 'written over' perceptually with new feature and/ore ideas, it seems the boundaries between each object don't melt away as easily. whereas trypts seems to make the objects go running away and the distortions cause the boundaries to become engaged as if reaching some maximum pressure. when you 'take a step back' with peas, everything seems intact and not flanging around like with the tryptamines. the visuals with peas seem to be climbing in and out of ones peception of the objects(or perceptions of non-objects), rather than the tryptamine 'climbing around ones' perception which objects tend to do.
i'm kind of picturing the analogy of there being a bunch of strings connecting you to the objects and symbols around you...it seems that with mescaline the trance and 'lizards climbing out of the capet'(yup i saw dat

) is some kind of perceptual engagement travel of investigating the strings' (though the strings themselves remain taut). i mean, it seems that the visions and visuals kind of 'pop up' into focus, or have a bent funhouse mirror quality, but the distortion is still bound to your perception in a linear manner. it might make a 2d surface become a mountain-like seemingly 3d landscape...but the 'drawing' is adjustments in perceptual recogntions of 'distance from observer'. like part seems closer than the other, and then boom! lookin at a mountain even though its just a table-top.
the tryptamnines, in terms of the string anaology are more focused on vibrating the strings themselves. so while the strings themselves may go investigated for their 'true nature' or a more defined analysis, the visual experience is most prominent in the undulations and flanging earthquake-like vibrations rocking the perception of the stimulus(or its an earthquake of 'real' waves being perceived out of the norm by the altered perceptual facilites..take your pick

). and like i said before, it seems the objects boundaries are more readily broken with trypts, they seem to bend and squirm in a manner which makes them 'appear' to move or travel across the 'field of your vision' even if only for a second. sometimes, they may make it across the room though lol.
while i can 'see waves' with peas...like, i've seen music float across the room..and i'm not talking synesthesia, i'm talking i could see the pressure wave which was the music, i could feel part of it entering my ear (with accompanying sliding tube sound effect of the sound traveling my ear canals) and i could watch the next notes of the music traveling from the speaker through the air (with accompanying sound of 'distance', lol 2ft is a lot farther than 2cm as its entering the ear). and i can also see 'heat waves' with mescaline, like the mirage kind of effect, but i can see it more sensitively with mescaline. i know its heat, because i tripped through that whole winter and the air was instead replaced with crystalline stillness. but depending on the heat outside i would see varied amounts of these heat waves. lol, i tripped and meditated through the entire year studying nature's pattern variation
anyways what i'm trying to say is that while seeing the 'wave nature' of light, sound, heat etc is a common effect of mescaline-vision, the overall perception of the world is not waving and flanging around. it seem mushrooms make me see the wave nature of sold matter very readily, or it tunes my antenna to some sort of cosmic radiations which are fucking intense and present anywhere regardless of earth-variations.
peas seems to put me in the highest point of my consciousness and very 'rooted' in a zen-like awareness. tryptamines, while definitely getting me to 'high points of consciousness' are much more 'keeping me on my feet' and always making me kind of 'come to' in some new dimension, like dream inside a dream. trypts seem to address paradoxes for me as well, or allow me to at least draw this philosophical mental diagram of paradoxes which obliterates my ego upon viewing lol. its like a philosophy adventure with mushrooms reading the riddles of the thousand year old woods and being shown glimpses into other dimensions...things of that sort. whereas, mescaline has a very solid and illuminating quality to its lessons, not so much riddles and puzzles as mushrooms often have it. the zen state of the mescaline-mind just observes and goes where it needs to go, learning what it needs along the way. the dizzy-go-round tryptamine mind is yanked towards the black hole, and it sees the information of a thousand eternities written on the smeared walls of the matter entering the event horizon :D