You plan routes and create them, and what you have actually traveled is a track. You can create tracks and edit them, but tracks are usually the info your GPS has collected as you ride.
Yes you can load as many maps as your internal memory and SD card will hold. I have all of my topo and National parks 24k topo plus the NT8 maps loaded on my Zumo. Just make sure when you upload the maps you want go to the SD card so you don't fill you internal memory.
They are selectable through the map info page. You can check/uncheck the maps you want to view etc.
Only issue is if the NT8 or 2008 that comes with zumo is selected you wont get the detail of the topo maps etc. So uncheck the NT maps and leave the map you want to display checked.
PM me if you want more detail....... Got to love the Zumo. I have 7 GPS over 15 years and it is by far the best one I have owned when it comes to riding on a bike.
'06 DL1000 Farkled