> The bigger difference is that the play store does not mandate using Google as the payment processor for transactions and subscriptions.

The rules have changed, they do now.

Fortnite was kicked out of the Google Play store for the very same violation of rules and consumer trust that they pulled with Apple. Epic are also suing Google under the same concocted story.

Google requires you to use them for payments, that's been policy for a while. (They do it because Apple proved you can get away with it)

You can always disable updates if you want. And what alternative stores specifically cannot do is install/update apps without having Android itself ask for confirmation again. So even if you manually order the store to install/update one or more apps, Android will pop up another prompt for each.