I believe it's generally the soapy toothpaste ingredients (sodium lauryl sulfate) that mess with your mouth chemistry and make things taste weird for a while af

I believe it's generally the soapy toothpaste ingredients (sodium lauryl sulfate) that mess with your mouth chemistry and make things taste weird for a while afterwards, not mainly the mint flavour. Other kinds of toothpaste (e.g. I sometimes use an aloe vera based one) don't have this problem. And my understanding of the before vs after breakfast teeth-brushing debate is that it doesn't that much matter which you do: do it before, and you clear off the bacteria that have accumulated overnight before handing them a load of food to work on; do it after, and your teeth are cleaner for the next few hours instead.