Errant is an interesting beast because it's a heavily revised sort of hard reboot of an older comic. But the absolute main crux of it has always been:
"Okay, so I love shounen manga, but the female characters are often kind of boring, or if they're interesting they get sidelined. So I'm going to make a shounen manga, but instead of a teenage boy, it's about an adult woman."
My fave shounen manga are probably Fullmetal Alchemist, Naruto and Bleach (at least, You know, Bleach up to the end of the Soul Society Arc. When Bleach was actually good. Honestly with Naruto I'd kind of say it goes downhill after the timeskip...arghh...). Plus Tsubasa Reservoir Chronicle, which had an impact on the art and the integration of that high shoujo drama into a shounen story.
There are definitely some more shoujo feeling elements to the storytelling (more than the style), I always loved the dramatic intensity and depiction of female friendship in shoujo manga.
In terms of how I time my panels and do visual storytelling, it's definitely Kiyohiko Azuma, creator of Azumanga Daioh and Yotsuba&! I'd cite as my biggest influence. I love his simple, yet dynamic, very clear visual storytelling and his comedic timing.
The writing I'd say my biggest influences are probably TV shows with ensemble casts. I think anyone reading Errant will probably peg me as a big fan of things like Buffy the Vampire Slayer and Firefly. Buffy in particular was a big influence with it being a modern story about a girl who fights monsters while having emotional drama and banter with friends. I also love sitcoms like Brooklyn 99 and Community, and even though I'd be the first to say Friends hasn't aged well, I was so hugely into it in my teens it'd be hard not to say that at least something of basing the story around a group of friends around a similar age who banter and have lots of drama came from a mixture of that and Final Fantasy VIII. I guess Harry Potter and the X-Men as well. I liked the idea of a bunch of magical people with quite grounded friendships contrasting the epic stuff they do.
Aaaand... obviously it's impossible for me not to say I love metamodern works like Steven Universe, Undertale, Homestuck and Dream Daddy. I love that sincerity mixed with genre awareness, and I also like telling a deceptively simple narrative on top of deep lore and characterisation. And being really gay.