For wifi without password you should look at WPS.
The "coffee shop" scenario, where a WPA2 Personal password is written where anyone can see it, is essentially as insecure as non-encrypted wireless.
WPA2 Personal is only secure if the password is very strong[2] and never given to untrusted parties.
The only wireless security I put any real trust in is WPA2 Enterprise with 802.1x certificate-based authentication specifically.[3]
[1] https://wiki.wireshark.org/HowToDecrypt802.11 [2] Otherwise it's possible to mount a hash-cracking attack after capturing the four-way handshake for clients that have the password. [3] WPA2 Enterprise with per-user password-based authentication is vulnerable to an "evil twin attack" unless the password is very strong, which is usually not the case, because organizations typically have it authenticate against Active Directory or another LDAP.
802.1x with a certificate for Radius server (TTLS mode, which simply layers the plaintext password via TLS) and plain passwords for users is also good enough.
Not a viable option, this would allow anyone to intercept traffic.
(To be fair, a lot of wifi routers are broken and will forward you all decrypted traffic from other users anyway on request. Try running WireShark on public wifis.)
The big problem is that Wifi with no password provides no privacy. Ideally we would have a wifi mode that is encrypted, but does not require a password. Just like Https.