So a friend of mine who is part of the Poppy Playtime dev team has confirmed that ALL bigger body experiments are children, therefore it's probably not the best idea to make NSFW of them or anything like that. It's not like FNAF where you can separate the child from the experiment since it's not a possession, the children are physically a part of them.
However.
Same friend also stated that the in-universe cartoon characters are all adults (aside from the Smiling Critters and probably Poppy too)
To explain it better...
(cw: slightly nsfw jokes)