Motorola Signature 27, since that seems to be the phone that is going to support GrapheneOS? I have a P10P, but I'm very excited that they are working with a manufacturer that actually supports them. I'll most likely buy the Signature 27 at some point, just to vote with my wallet (even if the P10P) is still fine.

Whatever Graphene or Lineage supports. Google doesn't even have magic power over all phone makers, let alone all ROMs.