I think if you're flying CO
all the way through you'll stay within Terminal C (I know some CO
flights leave from Terminal A but don't think MIA
is one of them?) You will still have to collect your bags, clear customs, drop them off again then clear security so it doesn't matter either way, it'll probably just take you 5 minutes longer if you have to change. Immigration at TC
is very quick though in my experience which is why EWR
is my airport of choice as there is less chance of missing your connection die to long queues.
As for smoking I can happily
say there are no smoking areas airside within the airport. You will have to go outside once you have cleared customs and get your fix there.
Food facilities in Terminal C are very good and much better than a lot of other US airports.
Enjoy your trip.