There are various kind of LED equipment: LEDs controlled by DMX or LEDs controlled directly with a LED electronic protocol like WS2811/WS2812/APA102 etc. (generally cheaper but not a lot of pre-manufactured hardware exists using directly those protocol, lots of people create their hardware including a digital LED strip, a plug etc. depending on their needs)
In case of LEDs controlled with DMX,
if you are in a small setup, a USB DMX is ok if you need only one universe (512 channel - 170 RGB pixels)
if you think you need more universes, a ArtNet -> DMX node is better. ArtNet is a network protocol to transmit DMX. You can control up to 32768 DMX universes (MadMapper supports up to 4096, people reported 1000 universes successfully from a single computer)
There are ArtNet -> DMX nodes with 1,2,4,8,16... universes.
In case you want to control digital LED strips, MadMapper will send ArtNet or sACN (network protocol) so no need for any USB or DMX thing. A LED controller will receive the network packets containing DMX data and will drive the LEDs with the appropriated protocol (you specify in the controller setup which type of LEDs you plugged to each output and how many)
Our blog is down but you can check our tutorials. Don't hesitate if you have more questions