Only one is required, to pass the data. You don’t need to use them all, in fact modern browsers prefer if you use less and just the essential. For privacy concerned customers, this is a better approach, to just use what is necessary. So whether it is 1,2 or 3. It’s up to you.
You also don’t have to use the parameters for what they are named, you could put anything, anything that is helpful for you to analyze. But do keep in mind, your analytics system may do extra analysis, based on the naming conventions.