Whenever I create my sims I always make sure they have the correct body type first before i put clothes on them. Is there a mod that will be default make my sims naked in CAS?

i am not sure if XCAS core mod by CmarNYC has a similar feature to make sims naked in CAS (it does not make sims naked by default) but it lets you tattoo sims naked and adds accessory options to the naked outfit. since i am using a non-core version of this (thats different) i dont know if theres a feature that let you design your sims better. maybe you want to check Cmars mod...
another way is to get you the naked outfits for sims as outfits that you can dress your sims with: ep. here at garden of shadows they work exactly like clothes

also i always found shaping my sims with underwear or swimwear sufficient enough. but if you need to see more check the mod or grab the "outfits"

Thank you! I have downloaded the nude tops and bottoms.