Note that there must be a ground travelling as a pair with the data connection as it passes from one strip to the next and of course that the supply and ground must always run as a pair. No separate wires. Particularly important in a car.
Lay it out, connect it all up and test thoroughly for 24hrs before fixing to the vehicle!
Should I put a 330R on just the first strip, as close as possible to the first LED, or should each strip have its own 330R resistor wired into the data line?
They actually do have tiny capacitors and resistors on the PCB between each LED pixel... does that change your recommendation for how to power them as far as using external capacitors and resistors, as well as power injection?
Solid advise!As a side note however, an automotive electrical system is nothing like the electrical systems you're likely used to. You will be subjecting the micro-controller and LED strips to an inhospitable environment.Huge transients / voltage spikes are possible and likely. This will take careful planning to avoid and mitigate.
Consider wiring all of the cabling for this well clear of existing wires to prevent cross talk. Add bypass capacitors (0.1uF) to the VCC line of the Micro-controller and the LED strips. This will reduce transients.
You also want to consider a circuit to specifically protect the micro-controller / Arduino from voltage spikes etc.
Where should I place the bypass capacitor, close to the Micro-Controller, or close to the LED strip?
And should each LED strip have a bypass capacitor?
... I put the 0.1uf bypass capacitor on the 4-pin line (along with the 330 resistor that will be on the data wire of the 4-pin line)?
Not sure what use those 0.1uF bypass caps will be, although I'm fairly sure they won't be harmful.
You seem to be distinguishing 2 pin and 4 pin lines. Not sure what the difference is. Aren't they all 3-pin lines?
I think the main reason for the delay in responding is that we all realised this is not an Arduino project.