Is it possible to allow only certain members to access certain pages? i.e have category "a" membership and access only category "a" pages?

To restrict access. You can set up 2 database

one to save “type” of members: includes : userId(multi ref from privateMembersData), products(multi ref. from another database called “product”

then, the “product” database, save all products same as the Wix example above.