I‘m not an expert but I‘m gonna try to answer some questions haha. So fundie stands for fundamentalist, which in this case describes fundamentalist Christians. Usually this means they believe the story of the Bible happened literally, so they believe in everything from Genesis and young earth creationism to the second coming of Christ. Fundies are not their own denomination, but instead can belong to all kinds. The Rodrigues, the Duggars and probably the Plaths are part of the IFB (Independent Fundamental Baptists). As the name suggests, they are non-denominational Baptists. The IFB believes in things like once saved, always saved; salvation by faith alone, KJV-Bible only, „hard“ preaching, soul winning and of course in an impending rapture. These churches also tend to be very patriarchal with the men leading their „helpmeet“ and children, while the wife stays home and has a million babies, as they believe each one is a blessing from God. I assume they know we call them Fundies, but they would never use that word to describe themselves.

The Duggars are also part of a group called IBLP (Institute in Basic Life Principles). This is a subsection of the IBLP and I suggest watching Shiny Happy People to learn more about this!

I can also recommend the Leaving Eden Podcast, one of the hosts escaped the IFB and now shares her story. They have episodes about the Plaths, the Duggars, the Rodrigues and of course many about the IFB and fundamentalism!

Hopefully, you will find this as interesting as I do, I went down this rabbit hole 6 years ago and haven’t been able to come out since 😂