I've made zero progress on Gundry as there is a checkbox which I think I need to tick in Particle Edit mode to make the bake show up so I can edit it, and it seems to be a guaranteed crash.  So looks like at this stage unless the new hair system drops sooner than I'm expecting it, I pretty much have to go the curve guide/soft body route.

Which means trying to figure out why my curve guides refuse to stick to their bone hooks and putting up with hair flapping around in anime locks (which at least won't be too terrible for this project because it's kind of semi-anime anyway).

And after Gundry I'm just going to be stuck in general as I don't have descriptions of the other characters, and the only other one I can do I'm not sure if I'm still doing.

For the Avian base model I'm currently trying to make a particle feather that meets my expectations.  This is the start.

Decided to try particle feathers following this tutorial on BlenderArtists. Got about this far in

and realised that I will likely need different mapping on each side because of how the particles are distributing.