Am I right in suggesting that the size of the vortex will be affected by the lift co-efficient the wing is under.

So high G turns and loops will generate bigger tip vortexes than level flight?

If you increased the AR of your pylon racer (keeping the wing area constant) the tip vortex would be smaller... but the wing would be weaker too (using the same profile).

You could mess around with tip devices like expander tips, diffuser tips or winglets, and even end plates but you are unlikely to get much improvement.

Eagles and Vultures can change their tip feathers to reduce wing tip drag at will - but that many feathers would mean just a few extra servos .