I am on the same level of expertise as you (i.e. it all makes my eyes glaze over :
) -- migrating to the same off-the main-computer photo storage system.
I talked to a very savvy LaCie technician who advised against making one partition of my new, large drive "bootable" Something about the fact that the computer might not automatically know which partition to reference on start up. In any case, since most of what's on my computer are small files now, I'm going to make the bootable drive out of one of my decommissioned smaller drives (a 250 gB LaCie).
Let me know what you find out!