Yes, with Re-Ment a sealed carton is a good thing! You will get a full set (unless one piece is switched out for a rare) as seen on the box. The 6-8 number means how many sets in small boxes are inside, the 1 means there is a possibility of a rare. There are no duplicates unless it's like a double set in two different color ways. This is usually the most economical and a lot of the times the carton its self becomes a small display.
There are no pin holes or hacks, just be wary of sellers who sell loose or open sets, unless you just want one individual set or there isn't/you don't care about a chance at the rare set because they're usually opened to look for the rare sets. And I do mean rare because in my 20 years of buying I've only opened 2 rare sets. (I think I used all my mojo on those colored pencils but no regrets)