Before crating a pwa, or simply generating favicons and icons to web app or website come here

This generates infinitely better results than manually creating them from scratch, and you can always edit the output to fix some non adequate behavior using this as a bootstrap for PWAs and favicons and app icons in general for your application.

Hop onto the real favicon generator, and get results better than anything you could do on your first try. Whenever I have to make those, I always use this tool and use it as a base for later editing anything that didn't go as pristine as it could.

This is a quick one, there is nothing much I can really add here, as the real favicon generator mostly do all the work and we are left just to choose options there, if I may offer just one recommendation it would be: explore all the options the site offers, as it can deliver better results.

Apart from that, consider donating to the tool, especially if you intend on profiting with the target of your icons, it's a free tool, and it's great, we vote with our money, and the people that make that tool do deserve it, if nothing else, just to help keep it running for the future.