A1) I'm not 100% sure of this, but I believe that if you purchase the shipped product that you will still have access to download the recovery environment's .ISO file through the store. I'll have to ask around to find out for sure. Good question. Of course you can ALWAYS download the installed portion of the product right off of the main storagecraft.com web page (it's called a "trial" on the web page, but in fact is the full product - it will work, with full functionality, for 30 days, or permanently if you activate it using a purchased product key).
A2) There is no difference in the software. I believe the boxed stuff includes a small manual.
A3) The ISO download is large (over 200MB). The installer download is somewhere around 20MB. Those are loose numbers, I haven't checked these sizes recently.