I was wondering, once F:NV Ultimate Edition has finished installing, is it okay to go and delete your regular Fallout: New Vegas Game Data Utility?

No, the game utility is the install which you need to play.

But there are two different files under Game Data Utility pertaining to F:NV. One is F:NV Ultimate Edition (over 7GB), and just plain F:NV (little over 4GB). I have to assume F:NV Ultimate Edition installs the core game in addition to the expansions as well, due to the install size being so massive (the add-ons themselves when combined add up to a total of around 3GB).

Again, not 100% sure because I can't seem to figure out for sure whether it's safe or not.