If you’re working with the WS2812B and need to turn corners, you’ll want to check out this NeoPixel Corner adapter PCB from josh.com. It’s a pretty simple board. I came across it as a solution for an upcoming lighting project.
In josh’s example, he used a CNC to mill the PCBs. If you’re using one-sided FR4, that might work well. You’ll want to double-check thicknesses if you want to use OSHPark or similar.
You can check out the full write-up here or the NeoPixel Corner Board project GitHub.
On a related link, this document explains differences between WS2812 and WS2812B.