What are your thoughts on going through your partner's phone? Do you think you should both be able to do it? Do you think that it's messed up if you do? Do you think it's a red flag? What are your thoughts?

I mean like if you got nothing to hide it shouldn't really matter, but still privacy

No, I don't think it should be. If my girlfriend would ask me to go through my phone, I would dump her right there. You don't trust me to not cheat on you? If you have to go through your partner's phone, then you don't trust her. It's about you, not your partner.