Depends on what your goals for the MVP are. The more you lean towards testing idea viability, the smaller the group and the less need for an actual MVP. The more you lean towards testing market viability, the larger the audience and the larger need for a full-blown MVP.
I’ve written a bunch on MVP, maybe one of these has what you’re looking for. I’d start with Should You Build a Minimum Viable Product, which talks about goals and whether or not to build. I think that might answer your question: