So, when you download tails onto a usb drive, can you plug the drive into a computer, boot NORMALLY, and access the files on the drive, or do you have to boot tails to access them?

So, when you download tails onto a usb drive, can you plug the drive into a computer, boot NORMALLY, and access the files on the drive, or do you have to boot tails to access them?
I'm not sure I understand your question correctly but a USB stick with Tails installed has typically two partitions: the first one, labeled "Tails" is a FAT partition without encryption and containing the operating system, the second one, labeled "TailsData" is an encrypted ext3 partition and used for persistence.
When I plug a Tails USB stick in my everyday Linux system I can open both the "Tails" partition and the "TailsData" (after giving its passphrase). If you're on Windows you might be able to open the encrypted partition using FreeOTFE.