Thanks for your comment!

It will handle 100,000s of cells without much issues: it has virtualized scrolling and rendering .

I have not tested it with large file sizes, like your 20mb or 50mb examples.

I would love to test the product with it. Is there a way you could send us an example of such a workbook, where data is anonimized?

You can send it to robbert@spreadsheetpreview.com