Hi Stephane,
Thanks for your interest in Syncfusion products.
2) By default, the text set in the Name property of columndescriptor get exported to excel sheet. The text set to HeaderText property, which even display in grid cannot get exported to excel sheet. There is no direct way for exporting HeaderText set to the column with the available GroupingGridExcelConverterControl. However you can workaround this issue by setting HeaderText to the range.Text property.
Please refer to the following sample in which i used a GroupingGridExcelConverterControlExt class derived from GridExcelConverterBase class for excel export. In this class, some code in ExportColumnHeader(..) has been modified inorder to export the header text set to the column.
http://files.syncfusion.com/support/samples/Grid.Windows/7.1.0.30/F80741.zipRegards,
Rajadurai