I haven't heard of this before. The name was curious "Pixel" so I compared it to the Google Pixel tablet and it's basically identical except for the WiFi chip. You could get a Google Pixel tablet for way cheaper and install Graphene. The Murena tablet seems like a ripoff and it has an account too (not sure if it's optional)
See if the Graphene team supports the 10 when it comes out. If it does then get that and if they don't then get the Pixel 9 at a discounted cost and put on GOS. Then wait and see what happens with the situation.
Calyx is okay but MicroG doesn't work nearly as well as GOS sandboxed GPlay. eOS tends to be multiple Android versions outdated. I'd go with GOS, Calyx, Lineage, then eOS.
Look at the list of available phones for each OS and verify that they can use the cell towers in the USA. Most will be able to. Calyx can work with Motorola phones that are cheaper than pixels but last I used Calyx which was years ago it didn't function as well as Graphene with their sandboxed Google Play services. Since you're just beginning I imagine you'll still use some proprietary apps and Graphene will make that transition much easier.
Unfortunately the media failed to load