Quick custom title question

[mymistica]

Hello, I was just wondering what the line between PG-13 and M is?
I was afraid to put what I wanted as my custom title but then I saw others that seem worse so I'm not sure.
Is it alright if I say what I wanted to put here or would someone rather message me?
Sorry, I just don't want to get into trouble as soon as I've been admitted.

I basically wanted to use the terms from Rihanna's S&M song, I'm just not sure if those terms are still considered PG13 or if they're considered M because they're a bit more... I don't know, not-vanilla?

[Beguile's Mistress]

You can post it here but that ruins the surprise.  You can send me or any other Staff member a PM, though.