That is up to you. LR website says: "You can download previous versions of Lightroom, such as Lightroom 6, directly from the Creative Cloud desktop app. You can have multiple versions of Lightroom installed on your computer at the same time, if you choose." I would make sure that the CC version is working with my current LR database before I uninstalled anything. I would also backup the CC database before uninstalling. Good luck with your new Mac!