It looks like you solved it, but posting the instructions here for anyone else with the same question:
To use with Pixelblaze, change the LED type to “Pixelblaze Output Expander” - then click on “Add Board” for each connected expander board. The interface will let you set up each channel’s start index and pixel count. A count of zero effectively disables that channel.
For more than one board, some of the cuttable jumpers need to be nicked with a utility knife (or anything that can put a good nick in the board). Each board has 3 jumpers that set an address between 0-7, which is then matched up in the config panel dropdown near “Board @ Address”
Here’s the chart showing how to set various addresses and which jumper to cut:
When using the 64 channel output expander, If you use 3 channels for 3 strips, do they just look like one long strip as far as the pattern is concerned? Or another way to ask my question - 3 channels does not mean 3 different patterns running in parallel, correct.? I guess the reason you need the expander is because neopixel strips get too long if you just keep trying to add more strips into one big long strip?
You can set them to a pixel index. You can make them overlap if you want, but usually will set them up as a contiguous array. Pixel mapping can give them 2d or 3d coordinates, or you can use the index itself in patterns to do something interesting.
You could have a pattern check the index and do something different for each strip.
Sometimes wiring would be more changeling, and yes the ws2812 has a data rate limit that will limit the FPS for long strips.