I have a project in mind that requires updating 9 separate 8" neopixel strips.
They are vertically mounted and their bases, where pwr/gnd/data connect, are about 5 inches apart.
I'm wondering whether there is an Arduino with enough appropriate pins to have 9 separate data pins devoted to driving these (and if having 9 pins doing whatever timing related stuff the adafruit library requires them to do will be manageable for the arduino)
The design of the mount for these makes it a bit hard to daisy chain them all together, and besides, I'm a bit worried about the data signal degrading over the wire runs.
A simple UNO should be able to drive this, you need one pin per strip. The pin is used only while you update the strip, so you have to decide if the MCU performance is enough for your project (we have no clue what you intend to do with the strips).
When the signal passes through each LED/chip it gets buffered/boosted so it can go through an infinite number of LEDs without degrading. "Long wires" could be a problem but your wires are not long.
Typically, with long runs the power sags so the LEDs at the end may be dim and the colors may change. So as long as your power (and ground) isn't daisy-chained you should be OK.
No, you’re wrong. The strips need to be powered with significant current (thus @Railroader warning), but the arduino pin they connect to is just “data” and draws no significant current.
How many leds does each strip have ?
You can use 9 output pins or you can concatenate all the ledstrips and use just 1 output pin. I would concatenate them.
What kind of pattern should they do ?
