romad wrote:
What is the ABC - Extended board? Also I remember an alternate US board but it is no longer there - was it removed when I updated to High Sierra? And what is the difference between the US and US - International boards?
ABC Extended is the same as US or ABC but allows a much wider range of accents to be produced via the Option key.
US and ABC are identical except the ABC does not have the American flag.
US International PC is like US but uses the marks ` ~ ^ " ' as dead keys to produce accented characters. To get the marks themselves you have to type a space after them.
Clicking on something in the Input Sources pane does not do anything other than show you the layout over at the right. To make a keyboard active you have to use the "flag" menu at the top right of the screen or a keyboard shortcut. You should definitely remove British and Canadian if you do not need them to avoid accidentally using them when you don't want to.