I know there are some "easter eggs" that shows all ladies in the game naked, but, if you don't find such easter eggs, the nudity level is low or moderate? (like previous games)

I think there might be at the nudist pool area. Maybe in the ballroom where you're under the pool.

There is a nude scene/pic for all the main girls in the game. And yes, all of them are easter eggs :)

In Drew's case there three possibilities even. Move leaf, don't listen and stand while she's walking. Now you only need to figure out how :)

http://larrylaffer.net/lslgames/lsl7-general/lsl7-easter-eggs