At max level you will only be able to conjure mana buns. There is no glyph to change this unfortunately.
The exception is time walking where you will conjure whatever level food your character has been scaled to.
As for whilst leveling, each leveling bracket has its own food. So this will be changing regularly as you level up.
As for a macro, just drag the food to your action bar. Conjure with the spell and consume with the dragged item. No macro necessary.