As an admin I wants to limit the products of a particular seller, eg: 10 or 50 or 100 products. Is this possible?

The admin cannot limit the number of products from each seller. But StoreHippo gives the option of approving or disapproving a product once the seller uploads it. You can also see the "pending approval", "approved", "rejected" products in your admin panel. 
All this will be displayed on your store admin page when you approve and publish the product.

Please refer to the following link to know more about the approval flow for seller products:
https://help.storehippo.com/topic/approval-flow-for-seller-products