>>114242241000 toys heavy industries synthetic human comes to mind as an artist thing, but they're hard to find or expensive.
Seconding romankey x cowl, there are some little things they dont do well but still high range of motion, shoulderblades are cool, shapes are anatomical, and having real ab crunch on females is nice. Their upcoming oni girl is thicc and cute. If you want any of their figures you pretty much have to preorder them though, or risk getting a bootleg.
Crazy Figure might be a good alternative to Romankey, they are very similar looking but I've never had one. People have recommended them here before.
Probably the easiest to find mannequins with decent range would be the Body-Chan/Body-Kun line from SHFiguarts, their newer ones are decent, any old ones should be avoided due to QA issues and trash design. Theres pokemon proportioned ones if youre into that, otherwise the sports have a good range, school life is actually good too. The Kentaro Yabuki one (the one in pic getting a boot to the head for not bending enough) seemed like it would be great coomer ref but is pretty bad in design and quality.
For belly squish/wrinkle reference, you might want to get one of the sex toys that has an ass and boobs and just bend that around. Or get a gf that lets you draw her.
I do enjoy silicone figures and wish I could recommend them but they require a lot of care and you can only pose them for a quick picture, they need to spend most of their time in a neutral pose or theyll get permanent pock marks and wrinkles, which really sucks if they're not a cheap one. The consistency is wrong on them for bellies and they dont really wrinkle up or act correctly. Less like flesh and bone, more like bending a tube of silicone thats on a pole, its just weird looking. It is great for boobs or asses/thighs, though.
