Not always, but often. The Red Dot is cheaper to use and that's one of the major attractions of reloading, isn't it. The economics is the same when you go to a slower powder, like from Red Dot to Green Dot or Clays to International Clays. You need more grains of the slower powder to equal the same performance, so it ends up costing more. I'm not saying that it's a bad decision to go with a slower powder, depending on what you want to do.
Many people feel slower powders give tighter core densities.
I'm just saying that it is going to cost you some more money to do it. As to which Texan bushing throws how much Winchester WST, I'd really be careful if you are just working off a chart. I highly recommend that you get a powder scale and weigh your charges even if you do manage to find a bushing chart. I never trust those charts. When I'm setting up a machine I always, always weigh what is actually being thrown.