it depends what you are looking to keep in the tank. a ai nano is prob a good choice as you can keep a variety of livestock/corals. if you were doing a few little fish it wouldnt really matter. all depends on what you would like to do with the tank. always better to spend money on quality item initially thought and not have to rebuy an item few months later
Go with a Kessil and goose neck. The shimmer is great for a nano that size and you can grow anything. For low light corals like rics and zoanthids I would go with simple led strips.
NO that. It's meant for smaller tank than the one you mentioned.
You need certain amount of LED power to light a certain size tank. In general, people use the AI Sol(if going for the same brand), which is double the power of the nano, for the size of your tank not the nano.