EmuNAND is definitely not needed anymore but you can use it if you want to. You are safe with a9lh if you only install System Updates while running Luma3DS. The only thing you shouldn't do is updating in Gateway Mode because this can/will brick the system. I also got 2 Gateway Cards yesterday and i will use them with a9lh in Sysnand because i only need them for cheats. All other things are done via Luma3DS. I don't use emuNAND because it's not needed and only a waste of Space on the SD Card for me.