Most "white-label" signing means your logo on someone else's page. For a platform, that is one level short. Your customers have brands too, and their signers should see them: every tenant with its own logo, colors, domain, and sender identity, none of it ours.
White-label works at the multi-tenant level. Each of your customers gets a branded experience: their logo, their colors, their domain, their emails. Not yours, and never ours.
Package, price, and sell signing as part of your product. Usage-based platform pricing leaves the margin, and the customer relationship, with you.
We sell through you, not around you. Your success selling downstream is the business model, so partner support is the product, not a program.
Start from the decision guide on standalone vs integrated vs embedded, or price the reselling model in the ROI calculator.