For #1, to remove the zoom box, uncheck the second checkbox on the "Selection Capture Options" tab, labeled "Show zoom panel under cursor".
For #2, can you elaborate on if the delay happens on every capture, even if you do multiple in a row.. or if it only happens if you don't use SC for many hours.
If it happens on capturing active windows, try unchecking the second checkbox on the "Window Capturing 1" tab labeled "Try to capture Aero Glass transparency effects".
If it happens only if you haven't used SC in a long while, you could try changing the "Inactive Memory Use" option on the "Startup Options" tab.