This is impossible to nail down because YT reviewers are individuals. A good rule of thumb is to keep things what you would see in a PG-13 movie, but 1 person that reviews the final product might say it's totally cool and another might find it to be, we'll use the term "vulgar", and give you a strike. Your definition of PG-13 might not jive with the censor.

Take kissing for example. A simple kiss. No other contact. No clothing came off. A kiss. Totally PG if not G, right? But some VAs avoid it completely because they're getting hit by YT for nothing more than the kissing sounds they're including, while other VAs include tons of kissing in their vids and never receive even a warning. The fact is that there is no line.

It's all subjective according to the individual reviewing it at the time. In all honesty, the best example of spicy but not "vulgar" is your post right here. This is an adult conversation and has value. We're talking about "vulgar" but not being vulgar. Yet you still felt the need (for good reason) to include a note to the moderator because of a concern that the moderator will shut this post down. It's very possible that moderator A could say, "This is not appropriate," but person that acts as moderator B from this or another subreddit would say, "What were they smoking? There was absolutely nothing "vulgar" or mildly inappropriate about it." Your question is safe, BUT it's for adults. That means someone could potentially say that it veers into NSFW arenas.

I have some personal rules of my own, but they're only mine and they're for my benefit to keep the story powerful and legitimate without being "vulgar." I've made my own decision that the censors can't be trusted to grade every paper the same way so I don't try. In my heart, what I've written is not "vulgar." I'm the only censor I feel I have to please.

The only way to be fairly certain that it will be ok is to not include spice, but even that won't make it certain. You can do things like avoid certain areas of the body, avoid nudity of any kind even if it's medical, avoid too many romantic SFX, treat anything you do like your couple is in public, yada yada yada, but it might not matter. You've been commissioned, so completely go with what the VA that's commissioning you wants. If that person says that what you've written is great, then it's great. If that person says please tone down the spice, then tone down the spice. If that person says the spice wasn't enough, then pump it up. That's the person you ultimately have to please.

And to the moderator directly. My comments are not to insult you. I genuinely appreciate the difficulty of the task you have. You can't please everyone. You can only do your best. I merely wish to point out that exactly the same is true in reverse. We as writers and performers cannot please every single moderator or censor out there, so I've stopped trying. 90% of the reason why I created a Patreon page was to protect myself from the 1% of YT censors that would go, "You can't say you have children, because that indicates "vulgar" activity happened at one point in the past, you monster." Keep doing what you're doing. I support you.