How to manipulate output on Server Action based on if / else?

As I understand a Server Action will be provided as JSON output. Now how can I manipulate that Output based on a conditional statement?

For example I have a users and they maybe got their PAID status. So he will see adverts with full information. Like name, street and phone no. Now if it is a UNPAID status he only will see a limited edition. How can I solve that via Serverside?

I see I can mask it via SQL but I will break the whole Query Builder when going with that solution: