I'll try to answer your questions. Tracking starts when the application is opened AND the Settings indicator is green. I wouldn't start the app until you're ready to track, but it's not a problem if you are. When you create the trip in SpotWalla you can control the start and end date/time explicitly.
Bubbler will record and buffer your locations as long as it can acquire a GPS signal. I believe the Lite version will only buffer up to 5 or 10 locations whereas the Pro version will buffer everything. Buffered locations are automatically sync'd to SpotWalla when it's able to connect.
You don't have to create a trip before you start, but if you want to share your travels with family or friends, you'll want to create a trip to share with them.