dave
your two cents might add up to four..
yes the shine is needed in most situations and the pearl will not have a bold stand out effect under a flattened clear. but it can be seen, again not with the same effect as the car you paint with regular shiny clear. as far as pearl in the clear versus pearl as base coat, under normal situations the pearl will look the same but you will have less build up (or should i say thinner tape lines) with the base than with clear, also you will not run into a problem with cloudy looking pearl, it can happen when mixed in clear because your clear does not allow your pearl to lay flat and balanced. pearl works off of light in two directions. the first is the light that hits it directly, the second is light that is reflected from underneath.. there for pearls always stand out the most over black. they become bolder and more radiant. so even with a flattened clear you will still see it is present...
the best advice is to spray a few test panels before painting the car. this way you can figure out just how much pearl and how many coats you need to acheive the desired look...