Ardour does not impose any particular ordering of tracks and busses in either the editor or mixer windows. The default arrangements are as follows:

In the Editor, the Master bus will always be on top unless hidden. Tracks and busses will appear in their initial order, from top to bottom. The monitor section (if used) will never be visible in the editor window.

In the Mixer, the tracks and busses will be displayed in their initial order, from left to right. The Master bus is always on the far right and occupies its own pane, so that it is always visible no matter how you scroll the other mixer strips. If a Monitor section is used, it shows up at the right edge of the mixer window, from where it can be torn off into a separate window.