Answer 1

KIVY

Pros:

Nice to be able to run natively on the desktop WITHOUT a simulator
Python is easy to work withUse (almost) any python library
Very easy to create custom widgets
Cons:

Default widget toolkit looks like Android 4.4. Requiring you use your own widgets or a theming kit like KivyMD if styling bothers youCreating dynamic widgets declaratively is not yet supported (loops for instance)

REACT.JS

Pros:

App startup is almost immediateBundled
app size is reasonable ~8 mbEasy to build and add / remove packages
Adding native modules is straight forward and intuitive

Cons:

The state "flow", flux, (insert cool name here) etc.. , whatever you call it is a pretty terrible implementation in my opinion. Why re render and diff the whole view to a virtual dom when you only have to change one text field?