When visiting this castle is it best to arrive early and go straight to the crown jewels as is recommended for the Tower of London? Also would Sunday morning be a good day to visit, or is every day equally busy? When you get tickets ahead online, do you have to commit to a specific time of day? Is it possible to leave the castle for a lunch break and return the same day?
No, it's not necessary to go to the Crown Room as soon as you get to the castle. Summer hours to the castle is 9:30am to 6:00pm. There is so much to see at the castle, you will enjoy it.
My wife and I were there for the first time in October. We didn't experience huge lines for the jewels as we have in the Tower of London. In fact, that portion of the castle was well laid out, so traffic moved well. There are smaller nooks of the castle that were much more crowded. We never expected to spend 5 hours at the castle but we did. It's amazing. I normally don't recommend eating at spots aimed at tourists, but the cafe within the castle had good food at not-unreasonable prices and a good view, too, if you can get a table near the windows.
Don't sweat this too much. The crowds just aren't the same as those at the Tower in London. That's part of the charm of Scotland. Take the time to take one of the tour that is offered. You'll get oriented to the castle and learn some history. I don't think that you can leave, but as someone already mentioned there is a good cafe. Don't forget to check out the war memorial.
Pam