Navionics Novice

I got my first bass/bay boat this spring and have been running a Lowrance HDS Live 7. I fish mostly in Arkansas and Oklahoma and the maps in the unit seem pretty basic, so I am looking to upgrade. I hear a lot about Navionics but I don't know too much about how it works. It looks like Navionics South Region covers most of what I want. I am considering two products, Navionics+ Large for $199 to HotMaps Platnium South for $199. Navionics+ Large covers all of North America, plus marine, HotMaps Platnum covers the south and no marine but adds satellite overlay/3D/Panoramic Photos.

Some random questions:

How valuable/useful are the satellite overlay/3D/Panoramic Photos from HotMaps Plus? I assume the basic contour mapping in 2D are the same for both choices.

Do they both come preloaded with everything? That is, suppose I have Navionics+ and want to fish in California. Do I have to download and install the California mapping or is it all already on the chip? That seems like a lot of maps to fit on one chip. 

If I do have to select and download the mapping for the lakes I want, I assume that is done through the website prior to loading the chip, correct?

When the 1 year subscription/free updates expire do I still have full functionality of all of the maps? 

Is a 7" screen going to be too small to take advantage of the Navionics resolution?

Someday I want to fish out of Venice, LA. It looks like I lose the marine mapping if I go with the HotMaps Platinum. I assume I can add Navionics+ later simply by buying it and changing chips out. Is this correct?

Thanks in advance for all the help!