For a 9am opening, DL lets guests in at 8. They can walk up the Main Street and congregate in the Hub, where there are actual ropes holding them back. At 9am they roll up those and there is a crowd of people heading to the top rides. Because walkways are narrow at DL, it can definitely be a funnel and if you aren't there by 8:30 you'll be pretty far back.
I would recommend just doing DCA in the morning. That park has the 2 busiest rides at DLR (RSR and GotG) which have FPs that run out quickly. The rides at DL still have FPs available well into the afternoon (even Space Mountain). The only FP that runs out is Fantasmic.