Ncard is an empty card for the Nintendo DS,it uses the GBA port as a USB connection,the r4 is simply a flash card reader.
No, the R4 is an end-all homebrew/backup solution for the DS. Get a microSD reader/writer (or a transflash adapter and an SD reader/writer) and dump some clean ROMs onto it. Whatever ncard is, throw it out. If you have an R4, you need nothing else.