Usually eBay will force them to give you a refund if you open a case saying the item isn't as described and you wont need to return it unless they pay for it
You will need to use CFW to play DLC as it needs signature patches unless you install using this method
https://gbatemp.net/threads/play-ssb-mk8-and-other-games-all-unlocked-on-sysnand-without-cfw-or-aocptcher.464178/
Are there converters available for other games not just BOTW as the switch has many remakes from wii u like MK8 and CTTT and it would be nice to transfer those over