Best is take downtime, shutdown application and do patching. You may have to decided between downtime and user accessing system. Which ever is having more importance should win.
But I would not see any advantage of users not accessing system.
As Pravin already said, you simply can take the application down before you start the patching cycle or after the prepare phase is complete (if you like).
The ADZDPATCH Concurrent Program will get submitted but it won't run and after you finish the patching cycle it will be cancelled. No harm done.
The application patches do not change anything in the technology stack components.
Technology stack patches can be applied during the online patching cycle.