Though I myself have never showered on yom tov, my son learned in Yeshiva both here and in E”Y that it is permissible with a change in the regular way, and if only done for the immediate cleansing (no long, protracted showering)of individual body parts. Hair washing is NOT included, particularly for people with hair of a length that water could be squeezed from it. When washing hair, you cannot help but be socheit the water as you wash it.
As to the smoking on Y”T, well that halacha (the heter part)likely came at a time when people smoked regularly (including some of the rabbonim) and it was not yet known about the health hazards both to the smoker and to the environment. Since the burning of fire for tzorech ochel nefesh was permissible, so too was the smoking considered as “ochel nefesh (ask any woman who has quit smoking and immediately gained thirty lbs. if smoking was not her “ochel nefesh”) Nowadays, all of us are presumably more educated and intelligent, and the layman as well as the rov knows that smoking is not only NOT ochel nefesh, it is mamesh sakanas nefesh, and therefore many if not most poskim would probably look at smoking as an issur for ANY day of the week, kal v’chomer on yom tov. Just my opinion.