My experiences with topping from the bottom align with what
@droptokon mentioned. Usually I find it manifests itself in overly specific requests, or steering play towards the action they want. The example I've encountered the most happens with submissive guys looking for female partners. They want a "mistress" to tell them how to play, but question and negotiate every action. In my experiences they have a script in mind and if the dominant deviates, the sub will try and steer things back to the script. One such encounter (long ago), I called the submissive out for the behavior, saying that if they had a script in mind just tell me so I don't have to keep coming up with new ideas until one sticks. This resulted in the sub saying there was no script, but that they weren't interested in what I was suggesting. Frustrating to say the least.
I think in my mind the difference between being bratty and topping from the bottom is consent and expectations. If you are a dominant with a bratty sub, you are more than likely prepared for your submissive to "misbehave" to get the spanking they desire, it's honestly part of your play. The misdeed is done in the name of play and in good faith, and therefore in my opinion is not topping from the bottom. Like others mentioned, the dominant often picks up on the behavior and modifies the outcome of the misdeed to go from the desired punishment to an actual one (e.g., the sub was expecting a spanking and instead had to eat a healthy meal). I've encountered bratty subs before, and knowing they were bratty I never viewed things like that as topping from the bottom; it was an accepted behavior based on the parameters of the relationship.
In the case of overly specific instruction requests, the intention behind it is not good-natured, but rather selfish. Regardless of how the dom/sub relationship is (bratty, trying to please the dominant, etc), when a sub makes hyper specific request without stating their intentions, I find that crosses the line. If you have hyper specific requests, like you only want to explore hot wax, informing your dominant ahead of time saves them a lot of wasted effort and frustration. It's okay to only like one particular kink as long as all parties involved are aware of that. For example, I thoroughly enjoy anal, but I do not like fucking my ass myself (personal reasons). When I explain my likes to someone I inform that that anal is a like, but that if ass fucking can be avoided I'd appreciate it. For me this establishes the boundary from the beginning so the dominant knows right away not to bother with something I don't like unless it is essential to the play session. I don't want to put them in a situation where they have crafted a wonderful task around fucking my ass only for me to say "no", especially because anal is a like (and in theory a task like that would not violate my established limits). Again, this goes back to consent and expectations.
I disagree with
@Magnetic' s point though. I do not feel that all woman fit the submissive role and all men the dominant. That is determined individually based on a myriad of contributing factors. Regardless, if you can successfully top from the bottom to me it means your top is trying to make things fun for you as well, hence why they are willing to compromise and find alternatives in play. I think
@Magnetic is referring to people who sort of dabble with the dom/sub roles, more of role-players than actual participants. They have a set goal for the play session because it's just that, play. They take on the role of the sub for the play but that is not necessarily their identity. Being a sub in that case is essentially a kink, something they choose to explore when the mood strikes. That's probably why in most cases the relationships don't last. It was never meant to. Being up front about your expectations or desires with your partner can help those who are serious about the lifestyle avoid connecting with those who just want a quick session to masturbate to.
Each person has their own description of what a dominant or submissive should be, but in the end all parties involved need to have a say in the play (this can even be giving up control completely to the dominant as that is agreed upon by both parties, or simply taking on the "dom" and "sub" role for a quick session).