@omegadragon Smut follows a josei-ish romance formula. And I can add that smut mangas doesn't usually draw the benises, and vagobas in detail or at all. Smut also has little screen time on the sex acts and mostly focuses on the romance part like dis.
E.g.
https://bato.to/series/81796/honey-love-girl-the-rose-cutter-and-his-love-slave.g.
Hentai meanwhile is more porn with its different tags and genre (anal, lolicon, BDSM, forced, deep throat etc). The genitals are zoomed in, there is an exaggeration of bodily fluids and boob to body proportion... Yos, the benises and vagobas are drawn very well... But mostly sometimes pixelated however there are some that don't. I've never really seen smut mangas with drawn diccs unless the scanlation group hires a redrawer.
E.g.
https://hentai2read.com/the_ogre_glutton_that_feasts_on_horse_cock/