In ascending order of esotericity:
Evagrius
Basically, they're really similar to me, physically, to the extent that a wacky hybrid animal with digitigrade legs, two tails, hooves, and limited magical abilities of outwardly not clearly not demonic (though they're in fact entirely not demonic) provenance can be. A bit more curvy and chubby, yeah, but that kinda happens when I'm designing characters, lmao.
However, what they actually represent is a combination of my ancestry, my history, some highly specific intense emotions of mine, and some degree of (trust me it's not mental illness bro no way). It's still the case that I've mostly created them for vent art and for very specific kinds of vore stuff with good friends, but having made a (currently incomplete but pretty close) VRChat avatar of them, they're also good as a character for when I want to be smaller than Katja.
(retired fursona)
They started out as non-fursona OC, became a fursona because… …actually, sorta thanks to a prolonged school project kind of thing where we were supposed to write about an OC several times over the course of the year. But I'd developed them a bunch because of that, and ended up with a character that represented:
just how basic and uninteresting my imagination and aspirations were back at the time. They were a bit of a power fantasy character, sure, but in a really wimpy, liberal way, which consisted of a ton of "no trUST ME THEY'RE REALISTIC" while relying on plot devices to effectively give them power.
Katja
Probably actually the simplest one: they're who I'd want to be were I free from the laws of reality. Shameless weirdo who uses ridiculous powers to make the world a better place, one friend (or stranger) at a time; also a friendly, self-domesticated cosmic horror with basically unlimited energy.
Dalton
When I eventually get around to making music, this is going to be my… mascot? They're Not Katja. Do not pay attention to how similar their design is to Katja's. They have never met a "Katja Antares". They aren't even 180cm tall, and they're also a ferret. How could they possibly be Katja.
"vaguely sorta Katja but hard sci-fi"
They're a thought experiment — "how could I make a character that's functionally similar to Katja, in terms of externally observable capabilities, while limiting them to technology that we can reasonably assume we'll have sometime within the next decade or so?". They're basically a horde of entirely interchangeable animal/plant/fungus hybrid cyborgs which are effectively thin terminals for a single mind.
A hypothetical Waluigi to Eva's Luigi and (hard SF vaguely Katja-like entity)'s Wario
This would theoretically be a hybrid of probably thirty-ish species across every kingdom of life who tracks my IRL shape so closely that I'd need to weigh and measure myself before drawing them, and whose capabilities would be limited to being able to regenerate themself from any sufficiently large collection of biomass they encounter — from some kind of highly resilient but still entirely destructible technological substrate, which takes the form of a backpack or something.
Narrative and thematic threads that show up in other OCs
I guess, like, if you really think hard about it, there's some correspondence between recurring things that show up in my Not At All Me OCs and more minor aspects of me?