Hi!
I believe that you are correct, everything derived from ParamWidget gets a tooltip by default and can be MIDI Mapped.
If you want to customize a tooltip beyond the arguments of configParam, create a subclass of ParamQuantity and pass it through configParam as described here: Configuring custom parameter display in v1
This was especially helpful for buttons that cycle through modes, as the tooltip just shows the button state by default. I made some custom tooltips that display a shorthand for the currently selected mode. Let me know if you want any more details, I have been doing this extensively.