Well, let's play a little bit with words...
Where the wing ends, out from the fuselage, or whatever, is the wing tip.
The 'plan view' (from above) shape of the tip is what we're really talking about, right?
Theoretically, a Hoerner, or Flite Streak type of outward form, ending in more or less a small point at the TE, leads the wingtip vortex outboard a bit. The vortex forms from air flowing outward from "under" and wrapping around to the "over" surface because the wing is producing lift. Pressure "above" is less than pressure "under." The outward flow is only a fraction of the flow in the direction of flight...
A square-cut tip rib, or a pretty rounded elliptical tip,or a Hoerner-type don't seem to make a large difference for our models. Just do what you like to do for reasons of prettiness or easy building or whatever. Tip vortices ARE there, and spoil a bit of the lifting ability of the wing's area. Some worse, some less.
Tip plates large enough to prevent this rollover vortex, so I once heard, would need to be way large. Some even claimed they should be something like a disc with a diameter the same as the wingtip. NOT pretty! ...or practical...