You'll lose any apps that use play integrity or other similar checks that check for a non-google OS. Some banking, media, or gaming apps may use those checks, but I haven't encountered many in the US. Other than that, everything will work as stock if you use the sandboxed play services. If you don't use play services, there's perhaps a longer list of things that won't work, including notifications for most apps that rely on FCM. The OS supports different types of isolation schemes like private spaces and additional user profiles. So you can find some middle ground on whether or not you want play services, which accounts are logged in where, etc.