Women generally wear a leotard over their tights, so they can be made thinner without worrying about "see-thru". Men's tights are generally thicker and don't have a little cotton gussett in the crotch.
Only you can determine if your tights are sufficiently opaque to avoid embarrassment. It is traditional to tuck in your T-shirt, and if you leave it out, anytime you do a releve' with your arms raised into 5th, it will lift above your crotch, so you shouldn't depend on that to hide the details.
>on the topic of dancebelts, can I wear a mens thong underwear in place of a "real" mens dancebelt?
There is no substitute for a "real" men's dance belt. Thongs are not sufficiently tight to hold your genitals firmly up and out of harm's way.[/i]