I've tried almost every class of hallucinogen there is. Psychedelics, dissociatives, cannabinoids. Never did get my hands on salvia, but these days I don't think I'm very interested in trying it either. I have the most experience with psychedelics and cannabinoids in terms of having tried many different members of the class. And I've messed around with some strange ones that don't quite fit into any of the classes, like zopiclone(the sleeping med). I've also experienced stimulant/sleep deprivation psychosis
Psychedelics for me usually involve complex geometric patterns, colours, and objects "breathing" and morphing. More distortions and extreme pareidolia than actual hallucination(defined as perception in the absence of stimuli). They also involve what feels like "enhanced" hearing, where you're able to focus on everything you're hearing with exactly equal attention(I honestly don't know if that description makes any sense), which makes music sound very different, especially music that's tailored for listening while on psychedelics, like Shpongle.
The cognitive effects are also hard to describe, but there's a a tendency towards tangential thinking while retaining the ability to navigate the complex tree of tangents, a feeling of profoundness attached to even the simplest deduction, and a perceived ease of handling highly abstract ideas. There's also a sort of tearing down of deeply ingrained biases and rationalisations which in my view is how psychedelics are potentially very powerful accelerants of psychotherapy and personal change.
I never liked dissociatives very much. Their effects on memory make it hard for me to even remember the experiences, and mostly what I remember from doing ketamine and MXE is that everything looks strange. Angles are weird. Headspace is more confused than profound and certainly less productive. I might just have an atypical reaction to dissociatives, idk.
Cannabinoids are very unique drugs in that they provoke some combination of stimulant, sedative, psychedelic, dissociative and deliriant effects. Many people report that after combining cannabis with psychedelics multiple times, their experience with cannabis becomes more psychedelic. This certainly happened to me. I used to frequently combine 2C-B with hash several years ago. Ever since then if I smoke some hash with no tolerance essentially have a psychedelic trip for 3 hours. I quite like it. I get to take a short trip into a psychedelic mindspace without the usual hassle, longer duration, bodily side effects and sleep disturbances of taking a conventional psychedelics. Right now I'm doing it once every 4 weeks, since I'm trying to cure my addiction to hash by teaching myself moderation, and it's been working fine. Although part of me misses just the simple feeling of being stoned, giggling at children's cartoons and eating peanut butter with a spoon. I suppose I might never get that back.
Synthetic cannabinoids are horrible drugs I wouldn't recommend to anyone. Their sheer potency leads to a domination of dissociative and deliriant effects. Psychosis is a likely outcome. Complete dissociation like forgetting who you are, anterograde amnesia, severe anxiety and paranoia. They're also quite hard on the body. Stay away.
Zopiclone is a strange one. It's primary mode of action is the same as benzos, but it also has some interesting interactions with nicotinic acetylcholine receptors, which I suspect is what causes the hallucination. It's the only drug that's given me tactile hallucinations, which is a strange sensation. If I had to classify it, I'd put it in the deliriant class, but it has some dissociative properties too. It's strongly synergises with cannabinoids but also with psychedelics. For me, the recommended dose of 7.5mg usually caused some very mild hallucination, but 15 was the dose I usually took. I don't recommend zopiclone though, as it can cause strange episodes of anterograde amnesia the day after. Even when used as a hypnotic. The Z-drugs were originally touted as being like benzos without the addiction potential. It's since been learned that they're exactly like benzos, addiction and all, just with more side effects. Boggles the mind that they're still prescribed at all.