I've been seeing those Choco kits and mentions of the plastica ones, but I can't find much info on them or what do you get (if they're garage kits, MMS-compatible statues, or whatever), despite seeing a few for sale.

What are all of the Choco kits? I love his designs

Usually the only place to find information on an artist's unofficial shinki mods is their blog.
this is apsy's blog, where you can find details of his items

http://apsy.blog.shinobi.jp/

and as per your request, here's choco's website

http://chocolateshop-float.com/

what you get tends to be insanely variable depending on the maker. Apsy ALWAYS provides you with everything pictured except the MMS body. Choco tends to do statues that are compatable (sometimes with significant mopdifying needed)

Thanks.