Since we still have nothing official from WDW (heck, they never even announced that reservations were open, did they?! WHERE is Marketing???), here's how things went at Pandora, which may or may not be helpful:
If Pandora was at capacity and had a line to enter the land, but you had a FP for, say, 3pm, you were allowed to skip the line to enter the land and go in at 3pm. A CM was stationed at the land's entrance and they would scan your MB to confirm your FP time, then allow you in. You could go right to your FP ride, or wander around, and you could stay as long as you wanted to after your FP time, but it was the FP that got you in without waiting in the standby line for the land. My understanding is that those with a custom avatar (the doll thing) reservation had the same privilege: skip the standby line and enter the land at the time of your reservation (maybe also Banshee reservations? I don't recall if they had those.)
With GE, we have no FPs, but I'd think WDW should honor ADRs for Oga's and reservations for Savi's and Droid Depot in the same way they did FPs and avatar reservations - and especially since there's a monetary hold associated with them. But, of course, until someone official says something official, we're still assuming and guessing.