Thanks, Frederick. Wouldn't w3tc notify you if it couldn't write to a folder, like it does when it can't write to .htaccess?
When you say Disk Enhanced is best for most, are you speaking of the Page Cache, or all of them? I currently have the Object and Database caches set for Opcode, since that's under "Dedicated / Virtual Server" and I have a dedicated server. I read somewhere that that was how it should be, but I'm not sure. (Minify is handled by Cloudflare.)