Getting started with Livescope?

Ok so I caught my first livescope fish last weekend. It was pretty dang cool.  Didn't have enough skill to dial in to see my lure, but anyway I got the gist of it. And we've had two top 50 texas bass caught in the past seven days, one on a lake that's, on a good day, not known for bass fishing. Gotta do it. 

Thanks in advance!

1) I don't understand the garmin head unit models at all, so I can't really tell what changes across the different models, and whether those models are worth the upgrade? I won't be able to run any other electronics, so mapping matters to me, if that has an impact. 

2) how much battery will I really need to run one all day with an 8" head unit? 10" just won't fit.  My helix is only supposed to draw .8 amp so a 10ah battery should run it all day, but that's really not how it works out, and drawing an AGM down that low kills it off pretty fast. But it is impractical for me to just overkill it and throw a giant group 28 at it. Any advice here? So I'll need the 8" head unit plus whatever the transducer draws, any advice on how to turn the mfgr rating into a practical size? 

3) considering pole mount vs on TM, I'm often in 15mph+ wind, so being motor mounted seems limiting.

4) what else do I need to know?