I think you have a wrong idea about GrapheneOS. You install the sandboxed Play Store/Services through their app store and then it's pretty much the same as any other Android phone. Except that it doesn't get in your face with preinstalled crap (Google, Apple, or Samsung). On the GrapheneOS forums there are a lot of non-technical people that install GrapheneOS and don't have many issues. The primary annoyance is Google's abuse of their monopoly with Play Integrity.

I would say it often feels more like a luxury product than an iPhone or Google-certified Android phone because it's not full of cheesy stuff. It's what iPhone and Pixel would look like if Apple/Google didn't want to push you: subscriptions, AI, movie/music apps, etc.

I don't think there's any defaults you need to change out of the box besides installing the apps you want.

But yeah, besides the stock Android which looks good, GrapheneOS does not add UI features themselves. When they add features like the recent secure clipboard, it fits nicely in the settings.