Hmm. Personally, I tagged my whole comic as mature because it'd be too much work for me to tag each update for cursing, F-bombs, innuendos, etc. (Young teens can intentionally look for it on their own via bypassing the age filter. I'm not their parent, so it's not up to me at that point. lol)
Even though I think that my story is appropriate for 14+, that doesn't seem to be a thing on Tapas. It's either G or M, which is a bit stifling imo. If you just have a scene like you're talking about that one time or maybe another time, I wish we had the ability to label the whole story as 14+ so that we still have a teen audience who is interested in reading.
I think if you have a LOT of scenes that imply sexual content, the whole comic should be marked as M. Especially any precarious angles, even if censored. That can get precarious. lol
For just a page or a once in a while scene, you can just let Tapas' bot mark it as M on just those updates. :}