@pit1 You can checkout Promoteplus (https://apps.shopify.com/promoteplus), Although do not have options to define the affiliate levels, but this can be achieved tweaking few configurations like defining different campaigns (similar to level) for users.
For second requirement, Promoteplus app work on the concept of cashback where referrer will get the incentives only if they also purchased the products (For having authentic referrals). Since incentive (cashback) is provided, in other term you are offering product from your shop as incentive or discount on product only. For any other question related to this, you can let me know.