Hello. Before I ask someone to install a shipping module, I'd like to ask some questions to make sure it is what I want installed, onto my ZC. I don't want to waste of friend's time (who is still recovering from sandy =\) if its not what I am looking for.

What is the difference between
A: http://www.zen-cart.com/downloads.php?do=file&id=1292
and
B: http://www.zen-cart.com/downloads.php?do=file&id=1267 (can this be used in version 1.5?)

Basically I am just looking for a USPS module that can give me current USPS shipping rates for the shopping cart. Also, are the rates for retail or commercial base? I am looking to offer USPS priority [non flat rate] mail and USPS parcel post, does either or both have rates for it (i tried searching for the words "parcel posts" in the support forums of those plugins, but there were no mention.. so i am just wondering)

If a customer checks out, I'd still have to manually create a shipment with the USPS right? Because I might have to change shipping costs of many orders on a later date (a lot are preorders) because its hard to know how heavy or big an item is before receiving items from my suppliers a few months down the road. I still would like to give customers some kind of correct shipping estimates because sometimes a customer may order in-stock items.

I tried to check threads outside of those support threads, but it is confusing what module the poster is talking about since posters usually just say "USPS module is bleh bleh bleh bleh".