I wouldn't say Junkrat is the easiest Defense hero to start with, his main attacks take a bit of time to get used to and he requires good knowledge of the map to use well, since you quite often want to setup at chokepoints and bounce grenades in weird angles to hit people hiding behind shit and stuff. I'd say Bastion is more straightforward. I would also argue that it's easier to start supports with Lucio than Mercy, he's more wellrounded and less reliant on your teammates being non retards.
Didn't read the descriptions for everything, but I assume they're mostly fairly accurate. That said, just try everything and pick stuff you like to play, it's much better than picking the "best".