I didn't expected Xenforo to be so hard coding. Not many options are available from the control panel in an easy turn on/off interface.
the conditional thing you suggest is to much information for a solution. I found this other post to be of better help. Thank you anyways for your reply.
Admin CP -> Appearance -> Templates -> EXTRA.css
Add this:
Code:
.LoggedOut .navTabs .navTab.members
{
display: none !important;
}
.LoggedOut .navTabs .navTab.forums
{
display: none !important;
}