We watched both from the upper right edge of this oval and I thought we had a great view.
We arrived 20 minutes before OUAT on a CL 9 day and found some room still in this spot. Look for the white lines on the pavement, because the CMs will not let you stop and stand in a walkway. That will help you see ‘open spots’ where you can stand and wait for the show.
The railroad has been recommended in the past for (the old) Wishes viewing. Both OUAT and HEA have projections on the castle and if you’re really far back, you won’t be able to see the characters and the scene.
You could possibly watch OUAT from a close vantage point and then backup for HEA if you’re ok with missing those projections and want to be closer to the exit. But we moved quickly (with a stroller) after the fireworks and still made it out of the park in front of a lot of guests.
Hope that helps!