Is there even a way to find out?
No, its impossible to figure out how many wallets are out there in the first place. If you are talking about addresses instead coinableS answers might lead to a solution. A wallet could contain a single address or many. One person could have created a single wallet or many. There is no sure way to know which addresses belong to the same wallet.
Yes, but if they are mining with a pool, this is sure to be incorrect, because the pool's wallet address(es) would be that first address.
Judging from this you are also not looking for miners - as in full nodes used for mining - but for people that contribute hashing power. Depending on the way the pool is set up their addresses are indistinguishable from addresses of people that contribute no hashing power to the network in any way, shape or form. Even if you know the addresses of everyone contributing to a pool, there is no way to know whether the person is e.g. sending the coins to someone else. That someone could contribute no hashing power to the network.
Overall I am not entirely sure what exactly your question is. Maybe I understood you wrong.