4k sectors. I don’t have a 25gib json file. Where can I get/generate the dataset you were using?

The dataset is internal, but if you get a bunch of web pages from wikipedia and wrap them into HTML then it give a rough idea.

With 4K LUKS sectors the write speed is too low for a modern SSD. Check that LUKS use a fast implementation. I have:

  $ /usr/sbin/cryptsetup benchmark
  ...
  #     Algorithm |       Key |      Encryption |      Decryption
        aes-cbc        128b       664.1 MiB/s      2615.9 MiB/s

and my LUKS setup uses aes-xts 512b.