I'm not sure that anyone will be able to answer your questions. Your credit situation is likely different from others, and there is no telling what happens when they crunch their numbers to make a decision. People can give you anecdotes about their credit situation and their dealings with Chase, but it may not get you any closer to deciding what is best for being approved.

I don't voluntarily reduce credit lines. If they decline my application, then I'll discuss my options based on the reason they provide.