I like a toasted bun rather than overly soft bread that gets stuck in your teeth though. You dont have to butter it and griddle it but if you do, you get the toast on the inside surface of the bun and its better for spreading on mayo and other condiments, but unless you burn it the bun is still soft, its just got more bite and structure to it.
Really, if your bread is too toasted like that, you probably burned it.
Mayo is okay but if its real mayo its gotta be in moderation. Otherwise, if its just more for the texture or so your burger doesnt seem dry (if its a kinda shitty burger, like from some neighborhood cook out and its overcooked)--if its just for texture, I like avocado smashed up and spread on instead, its a similar flavor but I dunno I get to feel like Im being bougie or some shit.
Mayo is also better if youre mixing it with shit--I like to add either sriracha, chili paste, or actual hot sauce to it. But using miracle whip should be treated like real for real terrorism because it is.