Yes, APO should be working fine, as the header above indicates the resource was fetched from the APO cache.
You don’t need a cache plugin, but it’s a good idea to have one. APO or not, every time a page is not on a Cloudflare cache, it will have to be fetched again from the origin, and a local cache helps with that.
You don’t need any page rules, unless you have a reason to have a page rule.