What kind of detail are you expecting? There are limits on what's possible using the sub editor parts and what the game allows (without modding).

Some parts of a modern nuclear sub will be irrelevant to Barotrauma, assuming there was space for them, and some specs will be top secret, the position of certain elements will need to be different, e.g. ballast tanks, due to the way the game works. WWII submarines will generally have a simple layout, one or two decks, which I've seen some of those U-boat workshop subs replicate quite well, as for the exact layout, I think some artistic licence with what's possible and useful in the game needs to be considered.