Android boxes also run on Android TV platform and have Google Play store and Google Play services available on them the same way as the android TVs do. The difference is just whether it is built into the TV itself or connected to a non smart tv by HDMI cable. The difference in the availability of the apps for one device compared to another in the same play store is coz of hardware compatibility. If your device has official access to a particular app you will see it in the play store, if not you can still side load it using the APK file through a USB drive or by directly downloading it using the inbuilt browser.