Android apps: let’s clarify.
Sailfish OS is not Android, but an alternative OS descended from Meego Harmattan; fortunately it has a module (paid) to run Android apps.
This “Android-Support app” allows you to run apps in .apk format.
Whether it’s a mainstream Android app from Aptoide / Aurora, or whether it’s a FOSS app from F-Droid, you will need the License to run the app.
Visit shop.jolla.com to purchase one of the available licenses. The average price is usually around 49 euros, but Jolla makes discounts on some holidays during the year.
(At the moment it is not possible to buy license and phone together).
If you already thought of staying Google-free, the basic version is fully working, with its native apps from Jolla Store and Openrepos.
Please consider that unlocking the bootloader and installing SF could void the SONY warranty.
BUT Not everything is lost: it may still be possible to send the phone to Sony, especially in the first year. Sony in any case is capable to repair the device (reverting it to Android).
The IMEI will be the reference for the SONY for international warranty.
Jolla-Devices does not provide an additional warranty to the Sony one, the item is sold as used by Jolla-Devices.