Do you want to allow your users to register using the s2members registration form and want to assign them specific member types based on their membership level? If yes, BuddyPress Member Types pro plugin can easily allow that.

The simplest way to do it is by mapping roles to member type. s2members will add a role for each level. All you need to do is to map a role(based on the level) to specific member type.

Now when the user successfully subscribes to a s2members level, they will be assigned specific member type.

For mapping roles to member types, please see this guide.