Depends on what you're used to using and comfortable with. I need wings because I lead an active life (lots of working out and Taekwon-do with tons of kicks and the worry about my white dobok!!!! lol). If you need wings, Y fronts, or briefs, whatever you know them as. If you don't need wings, boxer briefs would work fine too. But like Jay said, make sure they're not loose.
You can absolutely use tampons if you like. There's no rules regarding what trans guys use during hell week. Personally, I can't use them, dysphoria stops me, but if you can use them and are happy about doing so - you can go for them instead if you choose. The only rules that exist are safety rules - don't keep tampons in for too long (toxic shock syndrome risk). There's also menstrual cups you can use. They're reusable. You insert them also and then just empty them and wash them out when needed. They're not only better for the environment, they're better if you have any potential dysphoria about inserting/removing them if you need to do it less often.
