How to draw game graphics for iphone correctly?

Question

iPhone

Friends who are well versed in creating interfaces for i products, tell me:
1. For the game I want to draw all the graphics in vector, what settings should I set in AdobeIllustrator?
for example for iphone 5 I do this - (resolution 640 * 1136, RGB mode, ppi300 (max in illustrator) is this correct for the best quality? what pitfalls can be with a vector?
2. Each level will be scaled, (as in angry birds two fingers) in this case, do I need to make the graphics larger than the screen resolution or just draw the minimum scale at standard resolution (for example, iphone 5 640 * 1136) and the increase will already be processed automatically
? about this, I will be glad.
In general, I will be glad to all smart thoughts on this topic.
Thank you all in advance for your replies to this thread.