If you’re going to get the Blu-ray burner, you won’t need the blu-ray player with USB port. Do you already have a blu-ray player? If not, and you find one with usb (I don’t have recommendations, as I don’t have one like that), you can skip the blu-ray burner if you want.
As for the ‘purposes’, I just meant that there are other projects here and on fanedit.org where either blu-ray quality fanedits are made, or movies are preserved in their original format before some type of change was made (as with Star Wars), or the film was never released on blu-ray, etc.