Hi Brian,
Thanks for trying the new Outlook 2016 for Mac. According to your description, that your Outlook consumes a high percentage of CPU usage is more likely to be a client behavior.
Since our forum mainly focuses on Office 365 Online services, we have limited information to handle such client related issues. It is recommended that you contact the specialist Office for Mac Preview Community for effective assistance. We appreciate your understanding.
Moreover, since the Office 2016 suit is still at the pre-release stage, it would be highly appreciated if you could share your comments and suggestions by clicking the smile icon from the top right of your app screen. Our relevant team is looking forward to hearing from the Mac community and will use the feedback to finalize the product for official release later.
Best Regards,
Alex