If I buy tickets online, do they need to be printed, or will someone scan the barcode from the confirmation email as we walk in (in lieu of handing over a physical ticket)?

What Romeo C said that is exactly right. I know it is done that way through Fandango. I think you can also do it not only through Fandango. You can purchase your tickets on line, you don't even have to print them out. You will get an email confirmation with all your info including the tickets, (you might have to download them)and all you have to do is show your phone, and they will scan it from your phone. Make sure your have the tickets open on your phone ready for them to scan. Paperless. It's AWESOME and so much easier.

I know of you use Fandango, send the tickets by text to your phone. Then when you arrive proceed inside right to the ticket taker. They will scan the bar code and print the tickets for you.