I have no issues running them concurrently. Although I did a clean install, I did not uninstall MS Office 2011 apps. I am running a brand new Macbook Pro 9,2 with Yosemite 10.10.5. I have not had the previews, and I just updated to 15.14.0 (150911). I customized the install to include only Excel, Word, and PowerPoint.
I did a clean install of Microsoft Office for Mac 2016 from installers from my campus bookstore.