DMT effects receptors that are classic psychedelic (5HT2a), but also 5HT1a (or is it 1d - I'm currently baked 24hrs a day, atm, in an effort to get my phantom limb pain to fucking behave itself), but it's the same receptor that buspirone, the anti anxiety drug does. So, despite it taking you up like a Saturn 5 rocket, it is rarely tinged with fear. Get a big enough dose though (50mg), and when you start returning to earth, you'll be wide eyed & legless for some time afterwards (I've read a breakthrough dose is like barging into the presence of god. Pretty much guaranteed you'll be gobsmacked.
Salvia is a kappa opiate receptor, which while expanding, can be shit scary terrifying, as with bigger doses, you can forget you have taken a drug.
There are also dissociative psychedelics like ketamine. Not as head fuck laden as Salvia, but being a disembodied conscious can be a bit hard for some to assimilate.
Also, you've got to remember within the serotonogic group (DMT, LSD, psilocybin, mescaline etc.) there is a large variation between the subjective experience. The same thing occurs with the dissociative class.
Thing is, none are much like cannabis. I always found it a bit more anxiety ridden, when younger.
I could write a book on the nature of the variety of thedissociative state (people say I should, but they massively underest my laziness!), just as Shugin did with serotonogic psychedelics.
If you want, send mea PM and I'll describe the effects of different classical members of each group. A brief synopsis, because, as I said, I'm an inherently lazy twat