Hi @staskh,
Direct Subscription: If you subscribe directly through Databricks, you will manage billing through the Databricks account console. Payments can be made via credit card or invoicing, depending on your agreement.
AWS Marketplace Subscription: If you subscribe via AWS Marketplace, your Databricks charges will appear alongside your other AWS costs on your AWS invoice. This can simplify billing if you are already using other AWS services.
About your second question, you would need to contact an account representative to discuss about it.