When you share a password with a user who does not have proton pass you need to generate a link.

People with this link can always view the password when they open it. (You can put a time limit and a view limit it already)
My suggestion is that you can optionally put an extra password on this link.

That way the receiver needs a password to unlock and view the shared password(s).
If you by accident send the link to the wrong person they are still unable to see the login credentials because of this.
It's a feature Bitwarden has and I find it very convenient.