Do iOS 11/12 have special features making it easy to share Wi-Fi passwords between devices?
In my experience, both the names and the passwords are shared via iCloud.

If I add a Wi-Fi network on my iPad, and then go to my iPhone, it will have almost always already connected to that same Wi-Fi network.

If it doesn't, I can tap on the Wi-Fi name and have it joined, without re-entering the password on my iPhone.

A potential difficulty, of course, is if the 2nd device does not have a network connection. For example, if I have a Wi-Fi-only iPad, and I add a new Wi-Fi network name/password to my iPhone, then the iPad has no way of getting that information sync'd to it until it connects to a Wi-Fi network.

Hence my suggestion of connecting the iPad first, because the iPhone has its own non-Wi-Fi network connection with which it can sync new iCloud information.

(The same would be true if you replaced 'iPad' with 'MacBook' in the above examples.)