just added an example implementation in the xlsx viewer for search, but the code is yours to modify and customize. react-xlsx should expose the necessary functions to implement a custom search (by workbook/sheet etc...)
if you mean our docx viewer/editor specifically its hard to say without manually testing the visual fidelity with Word on some complex docx files
you are welcome to try it with your own documents and see, but its just one example we wanted to show. for the blocks that use the react-docx library, you can always copy the code and use a different method to render the docx file/thumbnails