Slax Core 6.1.2
Slax Xorg 6.1.2
Slax KDE 6.1.2
Slax Apps 6.1.2
Slax KOffice 6.1.2
Slax Devel 6.1.2
Slax FireFox 6.1.2
Which are the redundant items for using vbox on slax?
None are, depending on what you want to end up with!
However, if you mean that you are going to add 'Slax vbox' module,
then I would say keep Core & Xorg.
Apps, I believe, are for KDE, Firefox is your web browser, & Devel is for programming.
Koffice is KDE Office Suite.