“Is the only difference between Eikthyr’s Staff and the Lightning Staff their names?”

yes eikthyr's staff has a visual effect on the staff while the lightning staff doesn't have

The item effects are still displayed in English. Is it possible to translate that part as well using a YML or JSON file?

yes theres an example translation file inside the package you can edit that just change the name of the file with the language you will use and put it inside the plugins folder

I translated the item names and item descriptions according to the example file and placed the translated file in the appropriate folder, so those are done.

However, the item effects were not included in the example file, and they are still displayed in English. Is there a way to translate the item effects as well?

item effects? can you show me what you mean by that?

I can't attach images here, so I'll go to the Nexus Mods page and leave another comment there!

It seems I can't attach screenshot files on Nexus Mods either. Would it be possible for me to add you on Discord so I can send you the screenshots there?

yes just dm mo on discord

I sent you a DM on Discord, but I don't think you've seen it yet!

already seen it and replied just wanna reply for the sake of the points xD