The speeds thing you wont notice a difference if you get 54 or 108 for your internet connection it however will make a difference if you transfer large files, I would personally take whatever is cheapest as for a home network you dont need to rush transfering anything like you would in business and plus it adds cost
I never was very good at picturing setups but as far as I can see you just put the files you want into the shared folders and the other PC can copy them from there by going into the shared folders file. That is about the easiest way to do it. You can always get a program like switchback to copy the files for you automatically but it wont be that configurable.
As for the other question about which standard is best click here may be of interest.