I have all different kinds of panties that are very comfortable. I love granny panties because the fit in all the right places and they usually have a wide enough gusset to accommodate the boys. I say that honestly, but it obviously depends on the size of you package. I also have a number of stretch cotton or microfiber that fit very well. When I wear my pantie, I decide if I want to wear those that are so comfortable that I don't feel them at all, or if I want to be reminded that I'm wearing panties throughout the day.
As for G-strings, I've never found a pair of G-strings that can keep the boys from flopping from one side to the other. But, I do have some men's G-strings that are fine. The front is big enough to hold the boys, and surprisingly or not, after a few minutes, you don't even fell that the string in back is there.
I also have some Hanes cotton bikinis, hi-cut and grief made of very soft cotton and are very comfortable. Most of them are white so that they don't attract attention in the locker room.
YMMV