I've mixed THC-H, THC-B, THC-P, THC-O, THC-PO, ∆10, ∆8 and ofc ∆9 THCa crystals with more psychedelics than I've reasonably kept count of. They all act as a random coin toss of either increasing manic, frenetic every, or making it more chill, but it's very difficult to tell which will occur. I mixed different ones of these noids with mushrooms, DMT, LSD, 2C-B, DOM, ayahuasca brews, and a handful of stranger ethnobotanicals.
THC-B/THC-H and LSD, THC-O and everything, THC-P/THC-B with DMT, all of them with ayahuasca, and THC-H/THC-B with 2C-B stood out to me the most as shining combos, but many of them would've sent less "irondomed" people than myself or my boyfriend to the ER probably. I learned this lesson the hard way as many of my friends accrued what we now refer to as "psychic damage" from taking these combos, but tbh I love them.
Edit: I've literally never once experienced anxiety from a drug induced experience, a serious bout of brain damage in my past that had a million other effects probably contributes. I low-key suspect that my capacity to feel anxiety is fucked up in general. My hands have never sweat once, skateboarding comes pretty naturally to me, I've never carastrophized, etc.
But I also couldn't physically get jump scared for years after the brain damage (can now though), couldn't feel my hands or feet for ~7 years, etc, so there was obviously some pretty serious "restructuring" going on neurologically, I suppose. I just wanted to mention this to point out that I can't speak on any possibly anxiety inducing potential in other people, since I don't really experience it. People around me have enjoyed mixing these usually, but they're all the types of stoners who were smoking a gram or more of rosin every day.