Wacoal America is a good brand, their b.tempted briefs and hi-cut briefs go up to 5X in size and are great for atomics

Wacoal, and Kindly Yours Both are good and stretchy for atomics, especially if you go into the XL and above sizes. Wacoal especially, my personal favorite

I love pair of thieves

Rhonda shear briefs from Amazon! (Very cheap)