I would like to know, does the shape of the wingtip effect flight performance?
I am thinking about either slanting the wingtips from the bottom to top like are on most ARF wings or carving "vortex" wingtips.

If you do a search over on the "Aerodynamics" forum, you'll find several past discussions on this that will help.

yes,but you may not notice the difference.

Some of the best minds in the business have just come up with wing tip designs that produced the worst wing tip vortices and drag ever recorded!
There is a lot of bad science out there! There are many many opinions. I have fallen back on intuition. Make it look good, and it will fly good.

Well said Kingwoodbarney, well said.

Jetts