GrapheneOS has benefits even when used with Google Play Services. At least on the primary profile, you can install the Phone by Google and get good call spam blocking. Other apps that you’d prefer to be siloed can be put on another profile without play services.

Installing by piping from curl is pretty common and not a red flag in and of itself. Even Rust is installed this way. If you don’t trust the URL, you also shouldn’t trust any binary installers downloaded from that website.