Operator RNA and UI

I’m trying to understand better how the Operator RNA works together with the UI.

Operators (wmOperatorType) can store data in the StructRNA.

Am I correct that this is effectively run-time data?

It’s been suggested that the operator data is read only from Python and that I should use Toolsettings to store persistent data instead when adding new Tools. For some operators there doesn’t need to be persistent storage so it seems unnecessary to have to add this to the ToolSettings.

Is this correct?