I will be in Edinburgh in August. I hear the Tattoo is a must-see. Would like to know best part of the stadium to sit in. Also, tell me about the line to get in - it looks like it might be very claustrophobic. Is there some secret entrance or some way to bypass a big crowd? (Perhaps with a tour operator or guide).
Here's an older thread where seat selection was discussed. https://community.ricksteves.com/travel-forum/scotland/royal-edinburgh-military-tattoo-ticket-purchase-advice
As far as lines, yes there will be a line but buy your reserved seating ahead of time and you don't have to show up early just to stand line.
We went in 2012. I pre-purchased our tickets months ahead of time. There was a big crowd but I didn't find it much different than any other big event or concert. I would advise being prepared for all kinds of weather. Dress in layers, and if someone tries to sell you a pillow to sit on for a pound or two, buy it! The bench/seat will be much more comfortable if you do. :)