I would like to link from a registration form directly to a specific variant on a product page. I also would like to pass one of the fields from the registration form to the payments page. Is this possible?
Firstly… What is a payments page? 
And I don’t think it is possible to get a link to a specific product variant. Maybe if there aren’t a lot of work, you can make different products and then use their links.
payments should have been products. Yeah I think creating a product page for each one will be the answer just wanted to see if it was possible.
What do you mean “payments should have been products.”?
Can you link me the page you are talking about?