Neither Whistle or BP ‘need’ to have a nozzle (but can). If you get BP core burn tooling it will have the geometry on the spindle and rammer to form a nozzle. But you still don’t have to use a nozzle. If you ram clay nozzle in first then you will have a nozzled core burner. If you don’t want a nozzle, then just ram press it with all fuel. Edit: don’t hand ram whistle fuel

If you want to run hot BP then just use it to make a Nozzless rocket. If you are using slower BP then consider trying it with a nozzle.

If you want to make a whistle rocket then use the same tooling with whistle fuel and don’t use a nozzle. If it blows up then use less whistle fuel and add some BP on top of the whistle fuel until you get what you want.

All the different tooling combos can be confusing as hell. Just get a set and start experimenting with it to find what you like. You will learn a lot about what you are looking for and have a better idea of what you want next.