These incredibly small and slim surface-mount NeoPixel LEDs are an easy way to add a lot of very tiny (but bright!) colorful baguette diamond LEDs to your project. They are just 3.2mm x 1.0mm x 1.48mm and can be soldered in a few different ways: flat against a PCB, reverse mount using the top pads and a cutout in the PCB, and right angle. As they are pretty darn tiny, they will be difficult to hand solder. SMT techniques with solder paste and hot air will work best here.
The driver chip is inside the LED and has ~12mA constant current drive, so the color will be very consistent even if the voltage varies, and no external choke resistors are required making your design minimal. Power the whole thing with 5VDC, and you're ready to rock.
There are three LEDs inside, red, green, and blue. The RGB LEDs are controlled by a tiny chip that takes a 24-bit color level via the clock and data in and then does all the PWM control for you. So you just 'set' the color data once. Like all NeoPixels, you can chain them together, the output of one leading into the input of another for near-infinitely long strips.
Again, due to the size of the LEDs, they are not designed to be hand-soldered. They are really small, and the pads for the LEDs are underneath. If you want to hand-solder NeoPixels, check out the 5050 sized NeoPixel bare LEDs or the through-hole NeoPixel LEDs.