The old version, which you can find the info page for here, is limited to WS2812 and 240 RGB or 180 RGBW pixels per channel. RGBW takes 4 bytes per pixel, so fewer pixels fit into memory. If you configure it for more pixels than it can support, it won’t accept the channel data.
The new version can drive up to 800/600 pixels per channel, and also supports APA102 and can mix and match. Both APA102 and RGBW take 4 bytes per pixel, so are limited to 600 pixels.