After a Supercard can I play other cartridges?

Hi, everyone I am not new to emulation or mods
But I am when it comes to owning a Nintendo DS
I own a new Dsi XL and wondering if this Supercard is the card to get ?
Obviously no 3DS games needed or firmware that supports that system or games because I dont have a 3DS
I don't want to use the Supercard for the SNES or GBA emulators or media players or anything else
I ONLY want to play NDS USA backups
I want to know if this is the card for me ?
And I guess my real question is ---
after the firmware is on the micro SD card and inside the supercard cartridge
does it make new firmware on the actual unit itself ?
Can I take the supercard out of my DSi XL and still play original USA DS or DSi cartridges ?
I know my question may be lame but I'm asking because it's more about a child's gameplay not my own
Thanks for the help appreciate it a lot !

p.s. Is the firware easy to install ? yes I have read the wiki

Thanks again !

 

Thanks for the info so the R4i Gold doesnt have the firmware already built in ?
I need to install that onto SD card from their website I imagine - Correct ?
And once again I can take the card out and play Original Cartridges ?
So if I bought this card all I would do is drag my roms onto the micro Sd and start playing ?
Thats what I see from what I am reading about this
Thanks for the help you people are the best

also what to note:
I havent even opened this Dsi Xl unit or know firware version
Do I need to update the firmware of the actual unit before using a R4i Gold card?
Do install the firmware onto the Micro Sd card and for which versions do I get ? If I have the Dsi XL ?
Thanks for the info I'll be purchasing this ASAP