On a system with integrated graphics and 8 (16 logical) cores and 32 GB of system memory I achieve what appears to be optimal performance using:

    zramen --algorithm zstd --size 200 --priority 100 --max-size 131072 make
    sysctl vm.swappiness=180
    sysctl vm.page-cluster=0
    sysctl vm.vfs_cache_pressure=200
    sysctl vm.dirty_background_ratio=1
    sysctl vm.dirty_ratio=2
    sysctl vm.watermark_boost_factor=0
    sysctl vm.watermark_scale_factor=125
    sysctl kernel.nmi_watchdog=0
    sysctl vm.min_free_kbytes=150000
    sysctl vm.dirty_expire_centisecs=1500
    sysctl vm.dirty_writeback_centisecs=1500

I had considered some kind of test where each parameter is perturbed a bit in sequence, so that you get an estimate of a point partial derivative. You would then do an iterative hill climb. That probably won't work well in my case since the devices I'm optimizing have too much variance to give a clear signal on benchmarks of a reasonable duration.

[1] https://docs.kernel.org/admin-guide/sysctl/vm.html

I use lz4-rle as first layer, but if page is idle for 1h it is recompressed using zstd lvl 22 in the background

it is great balance, for responsiveness Vs compression ratio