I don't think this show has a pit, so most likely you have assigned seats. No matter what time you get to the venue, you will get the same tickets you would have gotten if you showed up at 10am. I think somewhere on this site there was a map of seating at Meadowbrook, and it showed which parts of which sections were for presale. Only 2 more weeks! :)
The Church Choir pre-sale tickets are assigned on a first-purchase, first serve basis (meaning the first purchase will get the best available seats of the price level they chose, and so on).
The difference would be if you selected reserved seats or general admission seats. The reserved seats will have a specific seat reserved for you no matter what time you arrive, while general admission seats will be first-come, first serve for that section. The general admission tickets at many venues are referred to as PIT or GA and may appear to have a seat number for capacity purposes.
Some of the answers provided above and many more can be found on the Ticketing and M&G FAQ page.
I hope this helps!