Back on the old alt.sex.bondage newsgroup some things were said so often they became acronyms, and one was TINOTW: There Is No One True Way. Also YKIOK: Your Kink Is OK.
In other words, whatever works for you is good. Set your BS detector to go off anytime someone tells you that "real" subs must do X Y or Z. You are a "real" sub right now, and you do what feels right for you.
To answer in detail: How much the Dom is in charge is entirely up to the individuals involved. At one end there are people who just enjoy occasional power play scenes, at the other are slaves whose Dom(me) controls every detail of their lives, and neither of them are more right or real than the other.
it doesn't have to be all about sex. I have had many part time subs who didn't want sex involved, and both of us have been happy with scenes that just involved D/s and power play. For me sex is the cherry on top, but I can enjoy the cake just fine without a cherry. Don't ever feel you have to pay for a scene by fucking someone you don't want.
Personally, I would never want a sub, even a 24/7 slave, to give up hir individuality. If I want mindless devoted obedience, I'll get a spaniel. And to be shamelessly intolerant, I don't respect Dom(me)s whose ambition is to make their slaves into robots. All ethical considerations apart (which they aren't,) where's the fun in dominating someone who can't even think of resisting?
And all slaves have rights outside of Fantasyland and inside the law, but some of them prefer to forget it because it spoils the dream. Another regular thing on alt.sex.bondage was the exchange where someone would say, I'm a real slave, not like you players, I obey my Master without any limits. And someone would ask, what if he wanted to kill you/fuck your children/cut off your arms? Well, but He never would. But if he did...? I submit totally because I know He would never abuse His power that way. But if he did...? Then it would destroy the trust our relationship is based on...
In other words, if he crossed her limits, he would no longer be her no-limits Master. It sometimes took a lot of back and forth to get there, but we stuck with it because we felt it was important to show the newbies that no-limits slavery is a great fantasy, but not a model for real life.
All just my not at all humble opinion, of course...