Someone else will have to answer regarding Amazon subscriptions, but as for Fictionwise:
FW used to have subscriptions, but has them no longer. People have been complaining about that.
You can, however, save a significant amount on back issues (generally up to 6 months' worth are available before you can no longer purchase them) by waiting for Fictionwise's discount coupons and buying the stuff then. I bought about a half-year's worth of old Asimov and Analog during their 60% off coupon sale for about $1.20 each for the single-month issues.
And you can re-download them from your archive at any time, even after they've "expired" from the on-sale listings.
The formatting is actually fairly plain-ish, as far as I can tell. I think they get sent to FW in some intermediate format that gets auto-converted to ePub, rather like Smashwords' Meatgrinder process. I haven't tried the PDF versions to see if they're any different (though I think maybe publishers can submit fancier PDFs if they've got them).
FW has some sort of service on their website where you can
send your purchases to your Kindle's e-mail address, but you have to be logged-in at the website to do it (but then you have to be logged-in at the website to buy anything anyway). And there's an associated charge at Amazon if you do it via 3G (but your profile says you've a K3 so you'll be using the WiFi anyway, presumably).
Hope this helps.