The default value is false. That is the one you get if you don’t specify it and ignore the warning.
Yes, it is recommended to add an @EqualsAndHashCode annotation on the @Data annotated classes that extend something else than Object. I cannot tell you if you need true or false, that depends on your class hierarchy, and will need to be examined on a case-by-case basis.
However, for a project or package, you can configure in lombok.config to call the super methods if it is not a direct subclass of Object.
lombok.equalsAndHashCode.callSuper = call
See the configuration system documentation on how this works, and the @EqualsEndHashCode documentation for the supported configuration keys.
Disclosure: I am a lombok developer.