As far as I know, this enclosures are preprogrammed to work with drives of one specific size, if your drive has two 1 TB drives, then, you cannot use any drive bigger than 1 TB. Now, this is at best of my knowledge…
Regarding your second question, you need to use the same brand that the box is shipped with, if inside of the box you have Caviar Blue, SATA I , then, you will need to use the same SATA I, Caviar Blue; trying to use another drive line will most likely end in “drive not recognized”.