Thank you for the lrztar tip
ZPAQ does deduplication on its own, it isn't a lrzip feature specifically
I don't remember how much difference there is between lrzip -z and zpaq, but I don't know if lrzip has the latest zpaq version integrated... And, for example, the Linux repositories (at least on Debian) have and incredibly old version of zpaq, which has a very poor compression ratio compared to the most recent release (v7.15, which can be downloaded from the official site: http://www.mattmahoney.net/dc/zpaq.html , or you can also get a pre-compiled 64 bit linux binary from here: https://archive.org/download/totaldoscollectionrelease1719811995_201910 the file is called zpaq_v7.15.zip)
I haven't found yet a way to compress games so much as FitGirl does, and she didn't want to share her method when I asked via PM
However here are some compression benchmarks: https://www.reddit.com/r/compression/comments/dkeshp/maximum_compression_benchmark_paq8px_is_the_winner/
Regarding cmix, can't try it since I only have 16 GB of ram