Hello,
Best would be to use the "product template" feature.
By using a template, you will unsure that all new products (created in the front-end) will start with the same data ; and if you do not give some accesses to the vendor, these fields would be pre-set with the values of the template.
So, if your template do have "ACL" settings, these would be automatically duplicate to all new create products.
Thus, you unsure that your vendor will create products with specific ACL settings, making the products not available for "public" but only to "registered".
Regards,