Look, You're asking very general questions. Air follows the same laws every time, but not every port applies those laws the same, bad ports don't respond to the same moves as good ones. So the general answer is, yes tapering a port is desireable as long as the big end isn't too big, & small end too small...but that needs to stop & transition at or before the bowl or pocket.
The higher & straighter a port is, the less CA & valve dia. it needs to flow the same air, and will do it at a higher velocity which = more tq & hp for a given flow. Just simply going by a "reducing CA as it goes" is a fallacy if a port sucks in shape, form, & bias.
All the work that gets done is to make sucky ports ( and that's a lot of them), suck less, so that the "ideals" can be applied as much as possible. A bad port likes bigger valves and CA, but that doesn't mean the intake runners need to be, since the port sucks it needs all the "pocket storage" it can get.
"Generally" that's about it.
