1) Open a new 3d project
2) Import HDRP
3) Run the Wizard
4) Edit->Project settings -> HDRP default settings

Try to expand any post processing effect like Exposure. Its not possible. So users cant even see what post processing are we applying by default.

Note:
I would suggest copying the HDRP default settings to the Assets folder (like sky and fog settings). This would also address the issue where we change some default value and users dont understand whats happening in their projects, why everything got brighter or smth. If they would want to update the default settings, they would need to delete their copy in Asset/HDRPDefaultResources folder and run the wizard again.