^Judging from my experience and reading users' posts the type of manic symptoms arising from 3-MeO-PCP or MXE use seem to be pretty good mimics of the symptoms people who are actually diagnosed with mania report experiencing. It's more complicated than CNS arousal, albeit blunt autonomic arousal can manifest in pretty complicated ways, too. There's a good quote from Andy Behrman on wikipedia's mania page that describes it:
"When I'm manic, I'm so awake and alert, that my eyelashes fluttering on the pillow sound like thunder."
Mania often involves this kind of amplification of sensation (an electrification of the world like 5-HT psychedelics), increased arousal (like straight stimulants), but also a kind of momentum of thought, ego, and feeling that can cause one to fly off on tangents in all directions with gross self-assurance, be they towards heaven, hell, or just some random far left field of consciousness.
Sometimes that momentum is so strong that it sweeps the experiencer along with it, and when the wave finally crashes they're so far from where they started that they've lost the plot (the NMDA antagonist mediated sense of disconnection from the body and amnesic effects probably makes one more prone to this aspect of mania than other drugs). [EDIT: once during a high dose DXM/MXE trip my internal monologue took the sound of the voice actor who read an audiobook I had been listening to in my car earlier in the day and I started to worry about the fate of the characters in earnest as if I was a part of the story -- thus literally losing "my plot" and substituting a fictional narrative from memory complete with alternate narrator]. Situations where this occurs may involve people elatedly resolving to completely re-haul their life while recklessly discounting the problems that arise from jumping into such an attempt blindly (granted in some situations such a change could be perfectly healthy, too, but recognizing the truth or falsity of that judgment in the first place may also be impaired by the manic state).
The ability to laugh off the ego inflation and delusions of grandeur you note during your use of 3-MeO-PCP sounds like hypomania, a milder -- and arguably much more healthy and useful -- form of mania where one's imagination can be swept along to fantastic hypothetical locations but their beliefs and perspectives remain more grounded. It's hard to pin down what mania is because it's so multifaceted, and can manifest itself through symptoms that seem to somewhat contradict each other, e.g. elation and rage.
While it's true that experiences of stimulants or psychedelics often contain characteristics of mania as well, I think the fact that 3-Me0-PCP and MXE bundle the qualities of stimulants, psychedelics, and dissociatives into single drugs allows them to better mirror mania in its totality.
