Can I go to graphene to check it out and then back to android 13 ? (Without a huge problem setting it back up?)
Yes, you can do it by the web browser easily, same way with installing GrapheneOS.
And a second question, I have a problem with SN PWA on this device. If I clear cookies and then go to log in to SN on the PWA again, which uses my Twitter acct, the browser freaks out. Not sure if it is the Google keyboard, or the browser (same behavior on both fennec and Firefox), or what. Not sure if that is just pixel 7 pro or all pixel, or whatever configurationa it happens on.
Might be application based, PWA's aren't their own browser but rather function like a browser tab in the original browser you set up the PWA with. Try logging in to SN first, then save a PWA?