By contrast to Plas, it seems like the stretching Reed Richards usually does is a whole lot less crazy-looking and more reserved, fitting with his different personality. So in the live-action FF movies, not too bad of an audience revulsion problem. Dunno how they'd ever manage a live-action Plastic Man, frex in a Justice League movie. Limb-stretching is one thing, radical shape-changing (especially doing stuff to the face) might get weird like you say.