Style and design principles are important in React Native to streamline the design and appearance of your app's UI. These principles make your app look more professional, effective and user-friendly. Here are some basic suggestions for style and design principles in React Native:

1. User Friendly and Easily Accessible Design:
User-friendly design ensures that your application understands users' needs and behavior and can be used easily. Easy accessibility allows you to design in a way that makes it easier for anyone who can access your app, especially users with disabilities. To achieve this, you can use high-contrast colors, correct font sizes, and easily clickable buttons.

2. Consistency:
Maintaining consistency throughout your app's design and styling helps users better understand and use it. A consistent use of color palette, layout and icons enhances the integrity of your app and gives it a more professional look.

3. Lean and Simple Design:
A complex design can lead users to confusion and complex experiences. Taking a lean and simple approach to the design of your app allows users to use the app easily and reach their goals faster.

4. High Performance and Fast Loading:
The fast loading and high performance of your application greatly affects the user experience. Optimizing images, anti-lag animations, and avoiding unnecessary data calls will help your app run faster.

5. Adaptive Design (Responsive Design):
A design that is compatible with different screen sizes and devices allows your app to reach a wider audience. By using Flexbox and responsive design techniques, you can ensure that your application displays properly on any device.

6. Real World Experience:
Using objects and design elements that users are familiar with in the real world in your app improves the user experience. For example, using standard design elements such as menus, buttons, and navigation layouts helps users understand the app more easily.

7. Testing and Monitoring:
Constantly testing and monitoring your design and style based on your users' reactions will allow you to make the necessary adjustments. By evaluating and analyzing feedback, you can continuously improve the design of your app.

As a result, style and design principles in React Native significantly affect the user experience and appearance of your app. A user-friendly, easily accessible, consistent, lean and performance-oriented design will increase the success of your application. Also, considering responsive design and real-world experience will increase user satisfaction.