For getting the 2 arches to act independently try setting the pixel count to 50 not 150 as every 3 leds equals 1 pixel with strips (count the chips not leds) As for flickering how long is the run to the arch could be data loss.
Edit: try 25 like Goliath said I read it as each arch was 150 but...
Update I have it working I used a 12v USB socket to power the wemos a stepdown converter to keep the power under 12v for the lights all working with wled now just have to add it in xlights and see how that goes
Thinking it has gone off topic but there is no charging from a car it is all solar set at max 13.8v but with fridge running etc it sits around the 13.2v at night when i will be using the lights.
I have jaycar up the road so thinking going this way...
they are 2811s and the vehicle is a caravan with solar input so at night it will have no charge and sits around the 13.2v maybe down to 12.8v depending on what is running at the time.
Hi I am looking at running some pixels from a caravan 12v system it sits at about 13.2v and wondering if this would be the go for dropping it to 11.9v to safely run the pixels.
https://core-electronics.com.au/dc-dc-adjustable-step-down-module-5a-75w.html
The pixels will be controlled by a wemos...
If I was to do my mega tree again I would go the roll. To do a 50x16 tree I needed to join strips as i could only do 48 nodes at 2 inch space so had to use more strip.