Sad to say that I encountered a webpage that failed to print searchable pdfs with Firefox or Chrome, but succeeds with Microsoft's Edge browser. I'm on Windows 10 and trying to print with either the "Microsoft print to PDF" or "Adobe Pdf" drivers.
Firefox successes in generating searchable pdf output for most webpages (e.g., this forum), so I think it depends in part on the page itself. An example of a webpage that I can not print as a searchable PDF using Firefox but can using Edge is https://www.covestro.com/en/products/newsletters/color-and-design/2018_10_appreciating-the-finer-points-of-color-material-and-finish
An example of a webpage that I can not print as searchable PDF using any browser is https://www.nytimes.com.
I expect the websites themselves are serving up content in different ways depending on the browser they detect, but I really have no idea. Experiment with various options.