If you install mint-meta cinnamon you will only get some duplicate entries but not a lot but if you install cinnamon you'll get a whole a lot duplicate entries and possible conflicting programs.
When I installed mint-meta cinnamon there was a conflict between nemo & Caja. Nemo hijacked my system placed itself as my default file manager. Same thing for my pdf reader Evince, two different versions of Evince and Gnome Evince placed itself as the default pdf reader instead of the Mate version. I can only imagine how installing the full cinnamon desktop would have done to my system.
It should run reasonably well if your system can handle it providing the quirks,annoyances I mentioned. It shouldn't damage your MATE desktop if things go wrong but you will have ensure you delete anything cinnamon if you decide to delete it later. When I uninstalled cinnamon using the software manager it didn't uninstall everything cinnamon installed. Thus it took a day or so deleting some applications like gedit,nemo,etc. I recommend using the package manager instead to uninstall if/when you decide uninstall cinnamon.
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