Custom VPN profile for macOS

But what happens when the user installs this profile?

It’s the largely the same as if they ran your app and manually saved a configuration for your VPN. After the profile is installed the user can use your VPN, either in your app, in Settings / System Preferences, or implicitly via VPN On Demand.

I know that now it's possible to load this VPN via my app, but what benefits I get from this?

Configuration profiles are usually used in a managed environment. The device manager installs the profile via MDM so that the user can use VPN without having to manually configure it themselves.

Another question - is it possible to create a profile for one of the native VPN on the Mac, and to create a Personal VPN app, which will use this profile, and do some things before connecting to the VPN?

No. Personal VPN and managed VPN are different things. A Personal VPN app can only see profiles that it created. A managed configuration can be seen by the associated app but a third-party app can’t be associated with a configuration for one of the built-in VPN transports.

At Apple Configurator, there are some built-in options at the connection type, such as Pulse, Check Point, etc.. What's the process of getting into that list?

There isn’t a documented process for this, so my recommendation is that you file an enhancement request and see how far that gets you.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@apple.com"

Thanks for all the detailed answers!