Separate the starting point from the extras.
Use a single-choice block for mutually exclusive base packages. Put optional additions in a separate multiple-choice block. That makes the structure of the offer clear and prevents someone from selecting two incompatible starting packages.
Let the price follow the choices.
Assign a numeric value to each priced option. Use a Result to combine the base price, summed extras and quantity. If an extra should only appear for one package, give that block a visibility rule tied to the relevant option.
Capture a configuration when it is ready.
A Send Response button saves the current choices and results in your page’s Responses view. That gives you the context for a follow-up. It does not reserve inventory, process a payment or send a confirmation email.
Keep the first version focused.
Start with the choices that really change the offer. Add a short description of what each package includes. Preview several combinations, especially any conditional add-ons, before you publish.