Specifically these come to mind for addWorksheet, writeData, and writeDataTable

• showGridLines
• tabColour
• borders
• borderColour
• borderStyle
• tableStyle
• headerStyle
• withFilter
• na.string
• firstColumn
• lastColumn
• bandedRows
• bandedCols

... or essentially anything else that could be used for formatting.

Further, the default options could be saved in an exported op.openxlsx for reference. If that is used, then the default options can be set globally with .onAttach() and a wrapper for getOptions() specifically for openxlsx can be used to simplify each of the calls. I'd expect that all of the calls to these would have to be reviewed to make sure that the global options set are checked first.