550 = NO o-ring, unless you want a new side case when the chain eats your existing one away. They're too wide. Standard 530 will work. If you need an o-ring, you MIGHT be able to use a 520.
Regular = regular links & regular lubrication.
O-ring = sealed links (with an o-ring on each side) and less maintenance (thus, a little wider).
Without getting into the details, 630 is heavier than a 530. 630 can carry more power to the rear wheel, but is physically larger.
You may want to change out the sprockets when you change the chain. A bad sprocket will eat up a good chain.
I'm sure more will follow.