I have no idea if you can use yellow or white onions in a recipe like this, but I don't see why not!

I also have NO idea why in the world every recipe has added sugar.  I would make these and leave the sugar out.  Who needs it and it certainly doesn't make a bit of difference to the pickling process.  I'll bet they're better without the sweetness anyway.  Who wants sweetness on a burger??  I also never understood why they put sugar in ketsup.  How weird. 

https://girlwiththeironcast.com/pickled-red-onions/