The constitution's actual standard for joining is general soundness in faith and a humble willingness to learn, not agreement with every point of Reformed theology.
Attending and joining are not the same thing. Here is the real difference, and the four-step process The Valley Remnant Church actually uses for membership.
A plain-language glossary of the words you will actually hear at a Reformed Baptist church, from the 1689 and expository preaching to credobaptism and the doctrines of grace.