Does reset all settings erase known wifi networks and passwords?

You are correct in that resetting all settings would not effect the password for an existing encrypted backup but resetting all settings would allow you to set a new password for future backups which is what I want to do.

From the apple support web site:

"If you can’t remember the password for your encrypted backup

You can’t restore an encrypted backup without its password. With iOS 11 or later, you can make a new encrypted backup of your device by resetting the password. Here’s what to do:

1. On your iOS device, go to Settings > General > Reset.
2. Tap Reset All Settings and enter your iOS passcode.
3. Follow the steps to reset your settings. This won't affect your user data or passwords, but it will reset settings like display brightness, Home screen layout, and wallpaper. It also removes your encrypted backup password.
4. Connect your device to iTunes again and create a new encrypted backup.

Thanks for the quick answer sergekills!

One more question: does "reset all settings" reset all email accounts and passwords?

I think you are referring to "reset all content and settings" which erases everything which is what you might use if you were selling your iPhone.

I am referring to just "erase all settings".