What would be a good size for the kastmaster jigging spoons for bass? I heard anywhere from 1/2oz to 3/4oz is the perfect size range if you're trying to catch larger sized fish like smaller bass and crappie/big perch.

I like 1/2 oz or smaller for bass.   I use 3/4 oz to target lake trout.    

I would suggest you try 1/4 and 3/8. I own many sizes and colors. Plain chrome is my favorite. They really catch everything. Here's what Acme suggests:

 

 

 

I’ve used the 1 oz size for jigging in 20-50ft of water

I tend to favor Little Cleo in 1/3 hammered blue and nickel. Two of my top five most epic fish catching days have come on this spoon. Switch out the hooks. I guess u go with what u have confidence in. Catch em up.

Depends on depth. I use 1/4-1/2 up to 30'