As for the cost... The plan is that all apps - iOS, Android, MacOS and Win will be part of Pro and Cloud plans. No extra cost. To buy separately they'll be $50 each (including 1 year of updates/support).
by the way if you are using a different host what happens when your pro plan expires and how do you renew it without any change in your app setting
If your Pro plan expires nothing happens - the PowerApps will stop updating but will keep working as usual. When you reinstate the Pro plan they will start updating again.