API Keys: Limitations and pricing

[PhilScovis]

https://developers.arcgis.com/documentation/security-and-authentication/api-keys/

We are interested in using API Keys as one mode of security authentication for our application, when users do not require user-specific access.  At the site above, it says

"Only ArcGIS Developer accounts can use API keys to read private content. ArcGIS Organization users should use OAuth 2.0 to obtain ArcGIS identity credentials to read private user content and access services on a user's behalf."

Does this mean that this functionality is not recommended for our users?  

Also:

"During the beta period, accessing private content with an API key is free. A pricing model will be announced in Q2 of 2020."

Was there a pricing model announced for use of API keys?  

[JustMe6]

I have a similar question posted at https://community.esri.com/t5/arcgis-api-for-javascript/access-secured-feature-service-using-javascr.... Really interested in possible solutions to allow restricted public access to secured features.  Just can not seem to get a response and that it appears to be all or nothing access.