Possession limit would be 20.
Don't believe there is a size limit, but gee you'd be hard up keeping small ones.
You may get a Crimson Banded Wrasse at a reasonable size (400 grm +).
You see Crimson's, Purple and Blue Throat Wrasse in Chinese Restaurants and they ask big prices so someone must like them.
Purple and Blue Throat Wrasse are not a species really caught in Sydney but they grow pretty big down the South Coast. 1kg plus.