AI File type for Character Rigs in AE - AI, AE Shape Layers or Rasterized AI to PSD to AE?

Yeah, definitely looks more like it would be distortion-based on PSD layers rather than creating layer hierarchies using native vectors. Future-proofing this may be difficult, though, as from what you show you'd heve to create new rigs regularly, anyway. Probably talking out of my behind a bit, but from the look this would likely even benefit from using a proper 2D toon software. Saw a bunch of tutorials on Moho and they seem to have quite a few things on offer for secondary animation, including physics-based simulation in the latest releases. Otherwise I suppose it becomes a matter aof splicing out the work in AE to create e.g. a dedicated project just containing the head animations in separate comps so they can be imported into other projects. In terms of resource usuage you should have no issues these days, even with expressions, as that has been acclerated a lot. Personally I'd be more concerned about stuff glitching out or data corruption. Ever since Adobe introduced hardware-accelerated functions everwhere this seems to happen a lot, so creating copies and backups should definitely also be part of the plan.

Mylenium

Well, no really good answer beyond the old "It depends." Without actually seeing your artwork and understanding what kind of treatments you plan to apply, nobody can give you a definitive answer. At the end of the day, all three workflows could be appropriate, at least for portions of your project. Clearly outputting a plain walk cycle to Lottie/ Bodymovin would be completely different from creating deformation effects like jiggly tails or wobbly bellies and then there's all kinds of things inbetween. See the problem? So rather than pinning it on specific file types and formats, this determination should be made on a case-by-case basis and even then if you were e.g. to use a rasterized PSD, you would likely still want to have the vector artwork in your project or opened in AI to copy & paste over masks or fix small things. Again, no universal answer here. We can advise on what you are willing to show and tell, but otherwise simply trust your experience and gut instinct.

Mylenium