The Graphene team think its flawed: https://discuss.grapheneos.org/d/24134-devices-lacking-standard-privacysecurity-patches-and-protections-arent-private/5

Cool your wife is into de googling! My wife thinks I’m a conspiracy nut. I have custom domains on proton and its been great, but with their moves toward AI and crypto who knows. I would probably try tuta if I was setting it up now - but who knows if they will eventually go wonkey then you will wish you self hosted anyway 🤝

If at all possible see if you can do wireguard yourself. Tailscale is basically inserting a third party company for no reason as its just wireguard with their servers involved. For example if you can run opnsense its easy to get running via the GUI. Very rewarding!