Loz,
I don’t know if any of this will help but it is what I have learned this year.
1. Since I'm casting and not trolling, am i better using a 200 series bandit or a 300 series? I'm worried that a 200 may not go deep enough to run closely above the brush. On the other hand, a 300 may be too deep? I prefer the 200’s and have been doing some trolling with cranks this year but this should hold true for casting also. I noticed the smaller the diameter of the line the deeper the small cranks tend to dive. Since you are fishing brush you may want to experiment with some of the super lines with there smaller diameter I would think they would work well and allow the bait to dive deeper. I have one rod with this type of line on it and I can cast further with it than the 4 pound Wally Marshall line I also use. Being able to cast further out past the brush pile and bring the bait back over it would give you time to get the bait deeper. I have also experimented with adding split shot sinkers to the line to get them deeper, this works but requires adding a little at a time to get to the right depth. I like to put the weight 1 to 2 feet up the line from the crank. Lastly and this seems to work real well so far is to use a drop shot set up on the crank bait. I do not think this will work well for you since the weight would be in the brush but it is worth mentioning. I am looking at the bottom depth, the depth the fish are at and running the weight on the bottom with the bait suspended above the weight at the depth the fish are suspended at.
2. Bandits seem to be the bait of choice, but has anyone tried the Wally Marshall Crappie Cranks? I use both the Bandits and the Wally Marshall cranks and can not determine one is better than the other, Bandits have more color options and I have some of each. My favorite is the Norman Cranks, simply because I have caught more crappie on the Normans. I know someone will not agree with this but in my experience color matters and I have two go to colors and they are both Norman colors that will produce when the others will not.
3. Any tips in terms of retrieve or other specific factors in successfully running these over suspended brush? I will be casting from boat docks and not from shore, so I'll be standing over deeper water. Check your PM I am sending you the info on the Normans I use.
I am not an expert by any stretch of my imagination but have caught crappie this year on cranks and noticed that I am catching bigger crappie with the cranks compared to the regular crappie jigs I use.