The TWebXLSX component will only link to a TWebStringGrid and a TWebTableControl. I'd think that it would be most useful (for exporting at least) for it to link to TWebDBGrid, TWebDBTableControl - or better yet TDataset (so it supports TWebClientDataset and TXDataWebDataset.
If it linked to TWebCustomTableControl rather than TWebTableControl, then it would support TWebDBTableControl as well.