it would be nicer if it was recessed to be at the same height as the counter surface when depressed. So you can have enough space to lay down large flat trays, etc.
There are no distance limitations in proximity to the sink. You do however have to account for the 4 15/16" lock nut that secures the pop up to the underside of the countertop, so keep that distance from a cabinet or wall in mind when cutting the hole.