Why dont you check out Ed Buffaloe's site unblinkingeye, there is a link in our home page. He has a very thorough article about Amidol and Azo.
As to some of your questions, silver bromide papers (enlarging paper) are usually very fast and do not depend on the developer for speed, so you would probably would have very similar exposures as those with Dektol. The color of the paper does have to do with both the type of paper and developer used. Amidol generally turns out very nice neutral colors with enlarging paper, azo comes out a little bit greenish but a dilute bath of selenium takes care of that.
Switiching to Amidol for enlarging paper is a matter of choice, some people think it improves their prints, some dont. This is something you will have to decide.
As with any developer the longer you leave the print in the bath it changes the tonal relatinonship, this is best described in AA book the print.
Last is hard to tell you your prints will improve 10, 20 or 50%. It all has to do with your printing style, etc, etc.
My personal opinion is that Azo is a very good paper if you like the silver look. I dont think is the magic bullet some people claim it to be the same way that pt/pd is not the magic process that will make all your prints look great. If you are an experienced printer then try it, if you are just starting I would recommend to pick a developer and stick with it until you know it very well and can make the prints you wish with it.