I've never used photochromic lenses, you're right they don't darken down fully inside a car (opticians promote this as a benefit, "ideal for night driving"!) and also they can take a while to return to clear when you go indoors from bright sunlight. I use polarised clip-ons to reduce glare off the road (reflected light is polarised), but you have to search around to find some with a very light tint. Of course it reduces transmission of any other polarised light as well, so some screens look dim.