2) I'm brown so while I could kinda mesh in the SHPE conference looks-wise, I'm not really sure if I'll stand out in the NSBE conference.. While standing out could be a good thing, would they look at it in a negative light that I'm "stealing" potential opportunities from black engineers or are they as laidback as they were in the SHPE conference?
You will stand out more, and you will, to some people look like an opportunist who may be "stealing" opportunities as you say. The whole reason those companies are there is to try to increase black & hispanic diversity in their companies, so even if you have luck scoring interviews just by being there, that does not mean you necessarily will have as good a chance as anyone in the interview process.
Rather than trying to game the system, I'd focus on improving your chances in other ways - get contacts in the companies you want, show self-awareness, have realistic but differentiated goals, show companies you have a passion for the field you want to enter beyond just dollar signs, etc.