Hi,
What do you need help with specifically? As you mentioned, you currently are overriding nodes that should not be overridden. The CAV page describes the final area:
/**
* Defines a node as final, so that it cannot be overlaid
* or inherited by sling:resourceSuperType.
*/
[granite:FinalArea] mixin
So the Pattern Detector is warning you that you are violating this mixin on the node at /apps/xxx/granite/ui/components/coral/foundation/form/textfield by overriding /libs/granite/ui/components/coral/foundation/form/textfield. I assume you've done this to create a customized TextField widget?