In other words, how many licks does it take to get to the center of a tootsie roll Tootsie pop?
If you are just asking how far can you comfortably go in real life with some sort of submissive/dominant fantasy, I would say that it really depends on a lot of different factors having to do with context. For instance, RJ (like my 2bx) likes her dominance on the dark side (black leather, dungeons, vampires etc.). I like mine on the lighter side meaning that I prefer a grinning "tease" over a scowling "torture". IOW, I like a sub/dom vibe but I don't really like much of a stereotypical S&M vibe. I didn't like it when my 2bx would put his hand on my throat during sex and when 6'5" GP said to me "Awwww, you have hands like a little 4th grader." and then lightly twisted my arm into an Aikido lock that verged on the scary rather than the sexy.
I know a woman who is seriously into being an S&M submissive in bed and I don't think that it is entirely unrelated that in real life she vibes about 20x more "too nerdy to f*ck" than me.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver