1- On deleting duplicate files of any kind, find the app called Singlemizer and follow its basic interface and it will give you a list of items that are attribute level duplicates.
I capture a lot of vids and profiles so often over a period of months may just accidentally grab same several times under different names. Sort by 'Wasted Space' and decide which version/ copy you want to keep. Once selected you can group dispose of said items. Still a partially manually function, but it works great.
2-On MacOS- the question is can the device be updated? Go to AppStore and Updates and it will automatically give you the most recent OS you can upgrade too.
However, as I just advised someone else:
I would be very cautious about the need to upgrade for certain items.
Sierra for me has been a serious disappointment. I held out 3+ years I think on Mavericks and frankly the faults and disconnects on Sierra have been a serious setback. I have a list about 30 items long of changes and failures (function and form) that simply do not make sense to an experienced Mac user.