The default of 50% quality bonus on a god module actually provides 500%. Changing this to 5 in the settings yields a 50% bonus. Something changed in 2.1, quality multipliers are now 10x higher than before. If I only want god module quality to provide a 5% bonus, I'd need to set it to 0.5 in the settings, but the settings don't allow decimal values it seems.

Related, but in the other direction: https://mods.factorio.com/mod/VFSteeperQualityWithMythic-fork/discussion/6a3ea5bf2020ee94ff46cf93

Confirmed on a local copy of your mod that dividing all the values by 10x fixes it:

    {
        type = "double-setting",
        name = "god-quality-module-quality-bonus",
        setting_type = "startup",
        minimum_value = 0.1, <== used to be 1
        default_value = 0.5, <== used to be 50, which resulted in 500%. I set it to 0.5 to get a more reasonable 5% bonus (better than a T3)
        maximum_value = 500,
        order = "a4"
    },

If you've got a github for this I'd be happy to submit a PR, I can also look into how to mask this complexity from users of the mod - i.e. not exposing the fact that quality must be 10x'ed in 2.1 from what's configured in settings.

Fixed in 0.2.18.