It’s really a fantastic tool and totally worth the literally $8 for the full creator version of this, so I’ll link you this tool. Just know that it gives you all the tools you mentioned in your post for free in its free version. However, you need a powerful PC, and a little patience, to use this because it’s made for VR:
Virt-A-Mate. See the forum post here: Virt-A-Mate. Free Character Making Game
You can expand your control over your characters’ fat distribution and shape (right down to the shape of their butt), get more assets (hair, clothes), and download pre-made models called “Looks” by searching the publicly available plugins for this software on this subreddit: https://www.reddit.com/r/VAMscenes/
Some of those plugins don’t work with the latest version, though. I have a number of them which do work, and they allow you to have more control over where your model gains weight and how big they can get. Your model’s realism is only limited by your skill and imagination.