For existing projects you probably have existing resource files, probably JSON files or java resources. For new projects you can ask yourself if you would choose JSON or java properties. Here are some pros and cons
JSON is a simple file format, supported by many editors.
If you use many different locales it can become complex to make sure all keys are entered in all resource bundles. You might need specialized editors to keep track of all translated keys.
It is not hard to generate your own JSON resource files from a database.
if you already used cbi18n v1 you probably have java properties files.
there are very capable (free) resource editors available for java properties.
Several web based translation facilities provide export to java properties and/or json resources