Periodic reminder from me that you can just get clothes for whatever size your body is. If you'd be more comfortable in a larger size, please do that. Wear whatever underwear you want, don't ever believe social media suggestions that you have to match, be sexy, wear thongs, whatever is the case. Same goes for any of your personal grooming. Who you are is not invalidated by any of that, no matter who you are, what gender you are, etc.
Personal sanity-wise, I am happy in full coverage brief underwear and cotton bralettes. Sorry but my ass is great and it's not because of a thong, and your ass does not need that either!! I prefer clothes I don't have to adjust, pull up, pull out of my buttcrack, etc. That comfort helps me express my best self blah blah