I can see how that's confusing. The "Joomla" setting is what you're looking for. Then, when you have the Social Profiles - Kunena plugin enabled, the Kunena avatar should be shown. Basically, the "Joomla" setting for user avatar will look through the social profile plugins and try to find an integration that has a valid avatar to use.
Try that and let me know if it works. If not, or you have other questions, just let me know.
Thanks,
Alex