Understanding settings for Project / Driver / Data Source

I want to start working with code styling settings in more detail but I'm never sure which settings to change.

I'm using BigQuery driver and have a source but the Code Style applied in the properties just says Default:

It doesn't allow me to change it to anything. Then if I go to Settings -> Editor -> Code Style, we don't really have Default. Does it mean that General is applied to that driver?

This one is also confusing for me. Is this a setting scheme or what exactly?

How do all those variables interact? :

• Driver
• Data Source
• Project
• Code Style
• Scheme