Hi M and welcome to the forum,
Yes, once you find approved suppliers in our directory all you need to do is contact them direct. You can of course ask them any questions you would like, perhaps prices on products, how to open an account with them and so on.
The type of requirements required by them to open an account largely depends on the type of distributor they are. For example, a wholesaler will always require a tax id to prove you are a business identity, some dropshippers will also require this, but not all. So if in doubt, just ask them and they will be happy to inform you of their account requirements.
Liquidators, no tax id required at all.
So it's really just about asking any specific questions you have. There are no right or wrong questions in my opinion, just ask anything that you want clarification on and they will be more than happy to assist with your inquiry.