[herczegzsolt]

I've not quiet worked with that long LEDs, but i have experience with 10-20m length indoor installations.

For our standards, we supply the strips with power at both ends and at every 5m in-between. (So an LED is at most 2.5m away from a supply). Your supply needs may vary significantly depending on the type of LED you use, these numbers worked for us on WS2812B 60led/m at 5V rail voltage.

> For long runs, do you prefer distributed power injection vs multiple smaller PSUs vs a higher-voltage backbone + local regulation?

Either should work fine, but when you use multiple PSUs or regularors, you may need to match their output voltage suprisingly precisely to get good results. A pair of thick copper wires is often easier.

> For addressable strips (WS281x/SPI/DMX), what are your go-to fixes for signal integrity over distance (grounding, buffering, differential, level shifting)?

WS28xx has built-in "reclocking" as long as your longest distance between two adjacent leds is <1m, you are absolutely fine. Be aware though that the number of chained LEDs impact your maximum refresh rate, which is an issue for animating. For a 60Hz refresh rate, you can't have more than ~250leds.

SPI is a nightmare over any distance. DMX is great if you respect the standard in terms of cabling and unit loads, but it i'm yet to see a DMX-enabled individually addessable LED strip. A DMX universe would be limited to 170 rgb or 128rgbw leds anyway.

> engineering patterns that scale and don’t become a maintenance nightmare.

Use a projector or a TV instead :-D