Setting up 2nd harddrive/data doubler

I just purchased the OWC data doubler to make use of the spare 320GB 2.5 internal harddrive I have just sitting around - I'm frequently running out of room on my 2011 MBP which has a 240GB SSD.

I don't think I'll have any issues installing the hardware and there are numerous posts and write-ups to assist if need be. I intend to install my iTunes library(250GB)onto the new internal drive and point my iTunes to play from it, everything else can stay on the main SSD. The question that comes to mind is:

-I intend to erase/format the new harddrive so I can ensure it is fresh and clear, ready to go, I assume but wanted to confirm that I should use the Journaled format?

-once the harddrive is installed I know that it is going to show up as an external drive. I don't have issue with this but am wondering if there is anything else that I need to be aware of, for examples issues that come up with a 2nd internal harddrive? Or any preferences etc that will need to be changed to reflect the 2nd internal harddrive?

-when I use Time Machine back up to my time capsule, will it back up both drives automatically or will I need to someone set up the 2nd internal drive?

Format the drive that's going into the optical bay using the Mac OS Extended Journaled file system.

The second drive will show up as mounted on your desktop. That does not necessarily mean it's external.

As for Time Machine, I believe you will have to set it up to backup the drives separately. I'm not certain of that but it makes sense that you would want to keep the backups apart from each other.