Yes, Trinity is full game plus expansions. And if you download it you can play immediately, though if you have the disc shipped you can still download the game and play.

Even if you buy it online, you can still have a physical backup of everything.  Archive copies of your game via impulse after you've downloaded.  Those archived files have a funny extension, but they really are just zip archives so you can extract everything and put them on a disk or not extract them and still put them on a disk.  In the future, say after a hard drive meltdown or something, just copy the disk back to your new hard drive and reinstall, no new downloading required.