>> Excel = matlab.io.internal.getExcelInstance
>> excelWorkbook = Excel.Workbooks.Open(fullfile(pwd,'test.xlsx'))
>> delete(Excel); clear Excel
Thanks to IA, your job is basically done! (Of course, this is essentially the same code internally as the other example, just nicely packaged in a set of callable functions by Image Analyst. You could pull bits and pieces from the class package and string them together "for purpose" to accomplish specific tasks if don't want to use the general-purpose routines.
I just checked the result of the above; the displayed number of decimals in column B of the above workbook went from 14 to 5 when reopened after the Save.
There's another function FormatCellFont that looks like can do whatever with fonts...with this outline and some trial and error, looks to me like you should have no real problems accomplishing what you're looking for.
Starting from scratch, yeah, there's a learning curve but if you don't "just dive in!" you'll remain paralyzed waiting for the perfect answer before starting.