Nexter is a very large block collection with more than 90 blocks. It works with any theme, but is often paired with the pro Nexter Classic theme or the free Nexter FSE theme. The Nexter theme is sold with Nexter Pro extension which includes a header and footer builder as well as a theme template builder. It also includes advanced display conditions. Nexter blocks work well in the Full Site Editor. Nexter Blocks Pro includes basic support for ACF custom fields.
The Nexter block collection has recently been rewritten to be very performant. The Nexter Pro extension includes a lot of extras, like support for code snippets, maintenance mode, and some security options. There are more than 1,000 prebuilt templates included.