Honor 9N is a bit cheaper than Honor 8C but however features a faster processor, higher resolution front camera and is handier. Honor 8C, on the other hand, has got a huge battery capacity.
Look at the detailed comparison here and choose the one made for you: Honor 8C vs Honor 9N
Yes, Honor 9N supports OTG. USB OTG or USB On-The-Go is one of the most recent technologies that allows you to connect your pen drives and in some cases hard disks to your smartphones and tablets. It has a cable and through that cable, you can directly view and use your pen drive in your smartphones.
You can also check the complete specs here: Honor 9N