For trunks/boxer style, I’ve found
Ergowear to complement my ass the best.
https://ergowear.com
I really like how the center seam down the butt accents my curves. I also find that more comfortable. I hate how most underwear is flat in the seat, pushing my gluteus together.
another brand that is very butt-focused is
D.Hedral
D.Hedral
Their Gigolo Joe briefs with angle fit do a great job lifting and accenting glutes, especially with the contrasting color stripe option. However, I found their briefs waaaaay too flat in front for me, since I’m packing both front and back. I have not tried their other styles, which seem to have more lighter, stretchy athletic fabric
the ergowear photo doesn’t do it justice, but gives a basic view.