The Android developer Settings guide is the best place to start before contributing to Chrome for Android's settings.
Many common utility functions that are useful for developing settings screens in Chrome for Android can be found in //chrome/browser/settings/android.
The widget subdirectory contains a number of extensions of AndroidX Preference classes that provide Chrome-specific behavior (like Managed preferences) or common Chrome UI components (like buttons).
The base Preference classes included in the AndroidX Preference library can also be used directly in Chrome for Android Settings screens.