Generic formula vs name brand?

So, I am aware you shouldn’t swap formulas a bunch and that little ones need time to adjust to new formulas. Our LO is currently on Similac Advance as that’s what WIC covers. However, as she gets bigger the amount we get won’t cover her monthly input and we’ll need to buy the extra ourselves. We can buy extra cans of similac at our local grocery store just fine but we also have a Costco membership and their generic version is super cheap by contrast. Is anyone else in a similar boat as us and mix-feeds generic & name brand formulas? I feel like most generic versions of things are the same or similar enough, but I don’t want to go messing up her little tummy if that’s not the case with formula.