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@MetropleX you MUST install ALL 3 packages if you wish to receive support for issues with sandboxed play services. The only package that can be installed without the other two is GSF to help with GCam as an example which doesn't require all of them.
Play Store IS NOT just a shop front, apps increasingly depend on Play Asset Delivery and Play Feature Delivery which require the official Play Store client instead of legacy OBBs which are deprecated and forbidden for new apps. Other Play Store services also require the official Play Store. Apps will increasingly depend on the Play Store for Asset/Feature delivery and other APIs.