For Word-to-PDF specifically, I'd compare them with an Indian-language document, merged table cells and pictures. Those were the cases that broke in my own converter when I tried drawing the pages with pdf-lib.

Rendering the .docx with docx-preview and using the browser's print engine preserved those cases in my tests. The cost was an extra click in the print dialog. That doesn't establish how pdfCraft compares with iLovePDF, but I'd want those documents in any output-quality comparison.