Yup, I read that but as I said, that ask me to be online and in the same firmware so that option is not viable rnHave you tried looking at this? http://en-americas-support.nintendo.com/app/answers/detail/a_id/27394/~/how-to-transfer-user-and-save-data
I know every game need certain Firmware update, but I know that in 3DS, even if the game asked for a lower firmware and one of the 3DS had a higher FW, the one with the lower gets updated without askingAlso, local play I think would depend on whatever version the game you are sharing, not the system's firmware. However, more updated versions of games can only be obtained on the higher firmware versions of the Switch. So, you would have to test any game individually.
Thanks for your response!