For Gt, Trevally, Queenfish and Bohar I would use the plugs that push more water and as a result you wind slower. That would mean that the front of the lure is broad- 20- 30mm across. These will come in a variety of weights and lengths to suit the outfit you are casting with and the size of fish being targeted.
For the bigger yfin that we get off of Cape Town I use a plug that is 18mm wide x 15mm thick and 140mm long. This imitates their prey of garfish or pilchard. I like dark green, blue or pink colours.
For the smaller yfin 10-30kg that shoal up more a smaller narrower plug works well. 15x14x120 in the same colours. This can be wound very fast and is ideal to throw into boiling fish.
Most plugs vary in weight from 40 - 100g with some at 120g. Remember these things cast like bullets so you do not need to go heavy. Lighter lures attract more bites as their action is a bit more natural. They tend to skip with less effort. The best word to describe the action you are looking for is slither. You should not feel the reel working hard to keep the plug moving.
I will try an post a pic of some of the plugs that I would take.
Kind regards
Anton