IME it depends on the substance... the ones I am partial to now like primarily lysergamides are relatively speaking doable to control and to more or less predict. With ETH-LAD i see a predictable tendency to give me ultra bad ADHD during some phase of the trip making it hard to finish a thought or write it down or make a diagram of my thought patterns. Efficiency is just crazy low, very scatterbrained but also playful and a lot of rick&morty like humor somehow. Also I get another predictable effect with ETH-LAD where things go in and out of focus, making it seem like things are soft toned or like there is some flowing viscosity in the air. All this combined with particular sorts of tracers.. Makes it really hard to get certain things done cause I just can't see (or thing) for shit - yet it's marvellous and super pleasant, one of my favorites.
Certain phenethylamines like the halogenated 2C-X are even more predictable in their superficiality IMO, there is tactile enhancement and things look embossed and amazingly Adobe patterned. However, although there are emotional components that can make it really pleasant socially or enhance nostalgia when seeing a movie from the past or hearing music from the past... on the other hand it feels quite artificial, puts me in great contact with my body in deep ways and can be dissociating (many psychedelics can) but the spiritual factor is hard to find.
There are exceptions like 2C-E which has a lot of depth and profundity somehow and 2C-T-7 which is severely unpredictable in terms of dose-response but lush and rich in pure experience. Pseudo-synaesthesia can really make for incredible effects that for me may rank super high on the list of reasons why I trip...
Tryptamines though are pretty unpredictable for me. I have no idea what mushrooms have in store for me, and 4-HO-MiPT for example can be alien and entirely surprising. One moment I can have black and white betty boop style classic cartoon CEVs and the next moment I see a mall out of which rolls a tsunami of extremely bright yellow saffran rice like stuff... I have had many 'random' visions on tryptamines. They have a certain style with much more entities / other worlds or alternate dimensions, but these tendencies while in a sense predictable (it really depends on how you look at it: the fact that mushrooms are so unpredictable is itself in a way predictable). As for OEVs: rather than just some photoshopped effects it is much easier for things to transform or just look very odd and Alice in wonderland like.. wondrous. So tryptamines IMO mess with the essence of things and not just via mainly sensory ways.
Last time I did ~20 mg? 4-HO-MET i hardly tripped at all but felt horrible like some super anxious reaction with allergy-like feelings, not sure if I timed it badly in terms of anxiety already in me... but I really hope that was a fluke. 4-HO tryptamines really boggle my mind and tend to be immensely adventurous. And in the past I usually found them among the most friendly ones on the body.
So yeah the dose-response curve and reliability of it also really varies per substance in my opinion. Some have a really steep curve at some sudden point like if you go above 15 mg 2C-E or even above 20 mg. Others like 2C-T's may have a really complicated metabolism making it unpredictable and depending on random physiological factors that have nothing to do with set and setting [i think].
Combinations also really potentiate trips and confuse how you think you react to dosage, and then there's also tolerance... Eliminate more of these factors if you want to get a better handle on your reaction, but it's also a matter of experence i think.