I don't know about food size, so I can't answer that one.
As for live and f/t, I'd take f/t any day, gut spatters included. It typically only happens, the guts, when you reheat a rodent more than twice, or leave it out too long. Other than that it really won't happen, so don't worry. It's so much easier to work around your own schedule with f/t, and less trauma to yourself, the rodent, and snake. Like I said, I'd pick f/t any day, and I used to do live. You -WILL- get some reject-ees in terms of rodents with live, and my advice is to have a little home for them in case this happens. That way you can keep them overnight until the pet store opens and bring it back, but it is a big hassle!
You'll also probably get attached to them if that happens. I know I did. It broke my heart being a rodent and snake lover all in one.
Anyway, thawing method: Stick rodents in a freezer bag, put bag in tub of hot water. Leave for ~30-40 minutes for a mouse at most, around 1.5 hours for a big ol' rat. I then use a ceramic heat emitter to warm them up slowly to a temp the snake will eat. Works well for me!![]()