For example, when I press on the button to increase the volume, IMO it increases the volume too much. I'd like for it to be 50% less than the default. Same applies for volume decrease. Is this configurable somewhere outside the widget or something? I don't see it in the widget config anywhere...
It's currently not configurable.
I currently don't work much on the Touch Bar stuff anymore, but I'll add a hidden default that lets you change it for all sliders:
defaults write com.hegenberg.BetterTouchTool BTTTouchBarSliderStep -float 0.05
Will be included starting with 4.272.
0.1 is the default
It's such a pity Touch Bar received such negative reactions, especially from tech people that should utilize it the most. I guess folk didn't understand the thing basically let's you behave like you're having Arch Linux right there on this small touch strip.
I think it was mostly Apple's fault for not allowing to customize it more or in general not realizing what people want to do with it.
Maybe it comes back in some other form at some point!