3/
All these projects are open source.
There are plenty of youtube tutorials you can watch to get an idea how to install them. But don't hesitate to ask!
Lineage supports the most phones.
Graphene supports Google Pixel Phones and Calyx supports Google Pixel Phones, fairphone and the shift6mq.
All in all, they are all great and beautiful projects which give us more freedom and privacy.
2/ with all the Gapps you want.
I can also recommend you CalyxOS, which runs google services (but doesn't have to).
If you care for longevity, LineageOS is the way. They support phones way past their official update cycle - it comes at the cost of some security once the security patches of your phone runs out.
Sorry if I went a bit overkill on the answer :BlobhajBlanketBlue: !
I think, they are not quite there yet for the moment and the average user (but I am by no means a dev. or fluent in code).
However, I can really recommend you to look at alternative Android OS'es. Here it depends on what you want.
For Privacy, the best one is GrapheneOS. You can have all google stuff (apps and google services) running sandboxed. And you can create multiple users for different purposes: like one for your daily use, with no Gapps, and another one 1/
🦈🐟🐋🐳 Biology student who loves the Sea 🐳🐋🐟🦈 (He/Him)