My guess is that the videos on YouTube are from a prior version of the client. It has been changed and streamlined.
In the current GUI, the green plus at the bottom of the screen has more than one function. If you just press it, it will start a new note. If you press and hold it, It will show you options for a new audio, photo, or reminder.
Adding a tag is done by tapping the "i" icon in an open note, and entering the desired tag
Here is a link with snapshots describing and pointing out where the things are that you mentioned in the iOS GUI