Welcome to AFF and congratulations to you and your partner.
A good starting point is
this article which explains the One World Classic Award. But note the points required is no longer correct as they increased last year.
This award is points based and does not require you to travel in a particular direction.
One World’s round-the-world product is very different. It’s called the Oneworld Explorer. Details of that can be found
here.
You can book your trip in different fare classes, but you’ll pay for the highest class of travel. In your case that’ll mean 455k points per person for First even if half your flights are in Business.