before playing I would like to know, is it better to play on hard for more sex animation? or does the difficulty not change the nsfw scene rate of the game?
If you dont know what your doing, you'll likely get a game over before you can enjoy the content of later floors.
Availability of many animations depend on Karryn's desire levels and some passives (i.e. learning how to initiate sex moves yourself allows you more options in the stall, not just battle).
Try playing the easy mode if you want to have an easier time viewing content without fear of game over (still possible to fail but very unlikely).
Normal is quite the challenge already. Only play harder difficulties if you know what youre doing and just want even more challenge or to do the extra challenges.
You should also look into how to modify the game settings, like removing autosave and allowing yourself to save whenever and on multiple save slots. This is good if you're trying to get a specific ending and/or keep virginity(s), or to avoid keeping unfavorable outcomes.
Main page has links to things like that if youre interested.