I think cow's milk is preferable to *toddler* formula from a teeth point of view - the formula is very sweet and more likely to cause cavities.

I have read that toddlers shouldn't have more than a certain amount of milk a day - this is because the very high calcium content of cows milk can block iron absorption and lead to iron deficiency.... I can't remember what that amount is though! Definitely food should be the primary source of nutrients, including calcium if possible (though it is hard to get toddlers to eat enough broccoli, etce tc for that to happen often!)

Good luck ttc!