Robotidy uses pyproject.toml file (which then is toml file). We're using the same approach as many Python tools are using - for example having tool.name_of_tool section in the configuration file. It's described in
https://robotidy.readthedocs.io/en/stable/configuration/config_file.html . If there is something missing or unclear please point it out, I always regard the documentation as most important part of the project and I would love to improve it :)
Your discovered bug with your typo :) - in most cases I try to have user friendly exceptions and print information if there is another parameter with similar name. For example:
3. "What is up with the _=_ in the config examples". Now I also see this in my browser, I will think about changes in our docs theme so it's not displayed that way.