There is something wrong with mozilla/css or fonts on my laptop, so I can't give a really long response (basically I'm typing blind now)

The method of switching between them is a long 'down' press, with the textual route display locked out until a route is loaded. In addition, 'No route loaded' is displayed in the graphical route display until a route is loaded.

Switching can also be done with 'down-left-down' i.e. there is a menu-option 'sats/map/text'.

Also the text screen is not locked down, that is the one that shows the no route loaded message. The graphical display has the large speed digits on the right and shows the track we've followed.