All matters dealing with gods are forms of belief. Nobody living knows for sure, regardless of how confident they are in their beliefs. The notion of a "religious atheist" makes no sense, by definition. You can say "rabid atheist" if you like, but you can't say "religious atheist."

I've been an atheist for about 55 years. I don't know whether there is a god, but I believe there is not. I don't attempt to "convert" others, but I'm perfectly open about my views when it comes up in conversation.