When you have multiple versions of the same sheet, when a field value is updated and saved, it will be updated in other versions as well.
On the other hand, if you have important constants or formulas that you would need to display results, but you don't want to display these values to other parties externally, you have the option to hide these fields with the hidden attribute.
This might be a requirement when you have to edit fields or values quite often, as you'll still need to refer to values in the hidden fields.
In the example below, the Internal copy has a few fields such as the profit that we're making, and the original vendor price that are sensitive, and will need to be hidden in the customers' invoice.
In the customer invoice, we can still have the fields that we need to refer to with formulas, but keep them hidden.