The connections are 3.3-5v, Data, Ground,
For rgb you send 24 bits representing the g,r,b values of each led pixel.
Each led pixel then consumes the first 24 bits it receives, and passes on any others it gets until it gets the reset bit.
For RGBW, you send 32bits per led pixel instead.
for ws2812 the max rate is 800khz, the achievable framerate is proportional to the length of the WS2812 chain, as it takes ~2.7ms to activate each led. so with 1 led you can get around 400 fps, but here’s a good article on the subject.