Welcome to the world of Simulink! I am glad that you've started by using our toolbox!
1. The model composition looks good, you delimited the configuration blocks from the action blocks.
2. The GPI read block will check the state of the selected pin and will return 1 if the state is high logic and 0 if the state is low logic. If you are expecting changes that are critical, you may want consider using interrupt blocks. For the outputs is the same behavior if you provide 1 to the output block, this will set a high logic state on the output pin and low logic state on the pin if the input of the block is 0.
Before starting to develop your project, I would strongly suggest testing how our blocks behaves using our examples.
Hope this helps,