I'm not into a big 'frontal' bulge. Most of my preferred underwear allows me to hang like I'm freeballing but keeps my package contained...That way I'm not accidentally sitting on something.
Speaking from the doctor’s point of view: we don’t care. If your trousers need to come off, anything underneath also has to. I’ve heard that one about trying on clothes before, can’t quite understand (an additional layer will change the fit, also you can’t appreciate how the garment feels when worn in a normal way)