Scots' main reason for considering independence is that the regime in the UK in the last 20 or 30 years has been increasingly foreign to Scottish values. They don't like the growing distance between classes, the 'austerity' values, the lack of egalitarianism.
If Scots vote to become an independent country, it is unlikely that any of the scenarios envisaged here will take place.

* Currency: a country can peg its currency to any other currency it wishes, and trade it at that value. Ireland pegged its currency to the British pound for a long time, and then to the EMU and then the euro, before joining the euro.
* EU membership: the EU would be only gumming to have Scotland - with a major chunk of the world's oil reserves, and rich fishing grounds, plus a vibrant financial service sector - as a member.
* Non-EU: however, Scotland could make an alliance with countries like the similarly oil- and fish-rich Norway, which has thrived outside the EU, while for instance Ireland's once rich fishing grounds have been fished out to barrenness by being opened to all EU fishing vessels.
(The EU's clumsy quota system means that fishermen throw back millions of tons of dead and dying fish into the sea because they're not acceptable within their catch quota. The EU's farm payments system has deformed farming and ruined small farmers, while chucking money and advantage at the ranchers who farm on an industrial scale. And the EU which was born with such noble promises that small and large countries would have equal advantage has become a Reich of bullying big countries.)