I prefer someone who is female as a straight guy and a sadist, but I understand they are few and far between.

I have trust issues; I assume everyone I talk to cannot be trusted or have alternative plans; as such, and foremost, I prefer to get to know someone and connect with them on a vanilla level. For example, hobbies, interests, politics, and having someone to discuss things with when things aren't happening.

As trust grows, so does information; I am not the one who will ever ask you what you plan; I think what is important is you are "sane" and able to make difficult and fair decisions, especially if it is a discreet desire to take "total" control that you don't reveal until it is too late.

When it comes to blackmail:

I do desire a safeword to stop things to chat.
However, I will accept the reason I provide may not be a good enough reason; as such, I may agree to you having a veto. For example, "I don't like it" may not be a reason.
However, I prefer an "Exit" word to end the agreement, and I agree that over time, this may change into some kind of "exit" task.
I do not desire or want exposure. However, I accept that, to a limited extent, it may happen or some kind risk on my side.
I "prefer" an unloaded gun option on real-life impact. Basically, you make me believe you will expose me to people I may know but never will.
Despite exit works, if there are things a Blackmailer desires/wants and desires to push the boundary but no real damage (If you are not going to do damage, but I don't know at the time) such as pushing one(me) to tears/agony, then I accept during play, I may hate what you do/ask, but as long one lands on their two feet safely at the end.
Financial blackmail, I rule it out as most who seek money are doing it for the money only.