If I have to be outside for a while in really cold weather I have long johns. But I don't have any regular underwear.
Briefs and there are several types. Both are made by Haines. I tried boxers. Most don't fit me well. My hips and thighs are too tight if I use my waist line. Regular boxing shorts with a drawstring work. Commando is an option under some conditions . .. especially at a nude beach
Nothing usually, especially in the warmer months. Or G strings. jock straps, as small as possible, usually see through or fine weave synthetics. My swimwear is usually as micro as possible and see through when wet. The ladies at the indoor pool in the clubhouse have never complained.
I wear men’s silk panties my wife loves them. I have seven different colors the black ones are see thur.