Remember what TSA screeners (and overseas screeners) are looking for - things that are a security risk only. Don't believe any of the silly stories in the media about screeners who are feeling people up or strip searching them - I have found them always 100% professional and focused, and the contents of your underwear (from a genital perspective at least) just does not interest them at all. Those stories are almost universally set-ups by activists who dislike "government" and think that "freedom" means they should be able to carry whatever they like on a plane, and they have gone out of their way to make a story where no story exists. If your ID is in order, you're good to go.
Just be smart – if your ID says you're male and you're a presenting as a guy, leave the bra full of wire at home that day. Things like that obviously raise red flags, not because it's someone who looks like a guy wearing a bra and they want to gawk and giggle, but because it warrants further investigation because it could be a guy with a bomb strapped to his chest. Metal near a guy's chest is odd, but near a female's chest, it's normal. The same would apply if your ID says you're female and you're presenting as female, but you have a packer stuffed in your underwear that might be filled with gel. If they frisk you, it will raise questions because it's something that isn't normally there.
But even if it does raise questions, they really have seen and heard it all before, and just a quick explanation that you're TG/TS would get you through that checkpoint quickly and discretely. It's not as if they get on the PA system and announce "Supervisor to checkpoint four – we've got a ->-bleeped-<-!" before hauling you off to a room where they put on the rubber gloves and go to town.
