Heavyweight Visual God.
I don’t deny that 12px can be harder to read than 18px, but I see a float label as an artifact of the past, rather than a clue to the future.
But just remember, a form alone isn’t going to boost conversion rates through the roof. You have to create enough value and solve a big enough problem with your content so a user is actually motivated to use your form in the first place.
React Native compiles your code to native code for the respective OS, either Android or iOS.