Can I show subscription plans of my audit platform, no prices, only descriptions, in my app, with buttons that navigates to my website, to buy there, without need to use In-App Purchases?
No. even though Google Play is more lenient about this but it is completely prohibited in both platforms Apple App Store & Google Play.
you can see how Spotify handels this in its iOS app install Spotify App and see how they do not even link to the main website of the service from the app because this is not allowed.
you can only show description and tell people to go to your website without linking to your website.