There's many guides out there for exactly this, but this one from QuinLED is probably the best [0].
You can't really avoid power injection downstream. I'm not sure if you're using 24v LEDs based on your ask (you said rails). But even with 24v strips at 20m you'll need 4A edge injection with 720 LED/m. This is literally one of the most simplistic approaches without being under powered.
Comments
There's many guides out there for exactly this, but this one from QuinLED is probably the best [0].
You can't really avoid power injection downstream. I'm not sure if you're using 24v LEDs based on your ask (you said rails). But even with 24v strips at 20m you'll need 4A edge injection with 720 LED/m. This is literally one of the most simplistic approaches without being under powered.
[0] https://quinled.info/the-ultimate-led-strip-power-injection-...