What security risk using iCloud Password? This option is to use my iPhone password in the Chrome and Edge browsers. Please explain more about this option, advice what risk if any activating this option and what benefit if any we have by activating this option.
iCloud Passwords does not save the iPhone password into the browser so that is NOT a security concern. The iPhone password is only ever saved on the device itself and is heavily encrypted and well beyond the reach of your browsers.
The Apple Password repository on your device does hold website login details for all the sites you access which may include sensitive websites like banking or personal file storage etc. The Apple Password repository is itself encrypted and can be unlocked on your iPhone with PIN or TouchID or FaceID but that does not mean that the PIN is stored inside the Apple Password repository.
If you allow Chrome or Edge to access the Apple Password repository it really only exposes your risk to the same login details as you can access via Apple Safari on iOS or if you share your Apple Password repository via iCloud you could also use it on any OSX Mac computer too. The advantage of enabling it is that you can login to Amazon, Bank etc on all the browsers and not just Safari and use your PIN or TouchID to unlock the Apple Password repository and load in the username/passwords.
As long as you don’t install a load of 3rd party extensions in your browser (Chrome on OSX being the most likely candidate) and keep your browsers fully up to date and don’t go trawling around the web on dubious websites the risk of your browser being the source of a hack is very small.