New to Arduino and forums so any info is amazing. Basic question and double checking so I dont damage neopixels and/or board. If I hook up higher than 5 volts, lets say 6 volts/9 volts to the VIN or DC in, respectively, will it down the voltage to 5 volts over the digital pins for output? i.e. powering neopixel strip. I know I can only use about 8 neopixels or so before I have to hook up external power of 5 volts source to power more pixels. The project Im working on will have roughly 150 pixels I want to stay away from the wall wart because the project I'm working on will need to be mobile and run off AA batteries or equivalent. That's also another aspect I'm reading up on but any info is awesome! thanks in advance!
The VIN is before the regulator it should be higher 5V (according the specification). In other words 6 or 9V is OK. On-board voltage regulator ensures 5V for the board, so digital pin high output will be 5V. But, pin output should not exceeds 20mA. It is enough to feed 1-2 signal LED. Higher current will destroy the MCU. If you need more power, additional power source is needed.
"The project Im working on will have roughly 150 pixels I want to stay away from the wall wart because the project I'm working on will need to be mobile and run off AA batteries or equivalent."
150 neopixels on at full white will draw ~60mA each, 9A total.
AA batteries won't supply 9A for long.