GrapheneOS is more strict about security, making it more secure but less accessible (at the moment you can only run GrapheneOS on Pixel phones).
I am happy with GrapheneOS' policy: that's exactly why I use GrapheneOS, to the point where I bought a Pixel just for GrapheneOS. Many people complain about GrapheneOS not supporting other phones. IMO it's the other way round: the other Android manufacturers do not support GrapheneOS.
If you really want GrapheneOS to lower their security in order to run on another phone, what you want is actually LineageOS.