@anotherthing, DS HomeBrewOS is the Ace3DS+ cart. I'm currently using my Gateway Blue card for playing some of my titles, compatibility is great but games with AP checks need patching.
No, I believe it's a yellow shell one. I watch that DNA gaming guy sometimes and he recommended a specific R4 cartridge. So I got the one he recommended, and that XXX in 1 was the exact one he recommended.
Great. There shouldn't be any problems adding them. A file called "theme.res" will be on the SD card, it's a renamed ZIP file so you can open it up with any ordinary software, such as WinRAR. Then add the icon to the resource file. You will need to make sure to specify it in the config.