Hi,
There is no setting. If you forbid products to be accessed by super admins, then they won't appear for them (besides the main products listing of course since you still need to be able to configure them).
CSV and mass actions are possible but I think CSV will take time, and mass actions won't be that simple.
I would recommend the first approach if that works.
Regarding mass actions, if you need to add a user group to all the products already with an access level, you'll need a filter on the "product_access" column containing commas in it. And you'll need an action "update the values" on that same column with an operation like that: concat(product.product_access, 'XX,')
where XX is the id of the user group you want to add to the products.
Make sure you do a backup before running such mass action because if you make a mistake, it could be hard to repair.