FastLED VS FastLED_NeoMatrix

I used the examples from here https://github.com/FastLED/FastLED/wiki/Multiple-Controller-Examples

Sweet. Then pretty much any arduino or other microcontroller would take care of what you need. The strips only take one output pin plus power and ground so just about everything will work for driving them. They act like a long shift register so the single pin is all that's needed to load the full strip with whatever patterns you want regardless of the length. You just have to tell it how many LEDs there are in total is all. Check out the FastLED library. You can learn more about it there and/or install the library in the IDE by pressing "ctrl shift I" for windows or "command shift I" for mac and search for it in the upper search area and install it right there. It comes with working examples too so all you would have to do is install the library, load one of the new example sketches that came with it, and probably edit the example to change the NUM_LEDS count to match what you're working with.

For tiling, you'd have to extend XY(). This is simple enough for the case of non-rotated, raster-layout tiles. Adding more flexibility adds quite some complexity. You end up with something like NeoMatrix.

I created a 16x16 LED matrix with WS2812 LEDs connected to an ESP8266 (NodeMCU pro mini). I'm using Neomatrix_FastLED to drive the matrix, which uses FastLED as the "driver" of the LEDs. Now sometimes the first Pixel in the Matrix LED[0] shows the wrong color (in my case red) and is randomly blinking. I read a lot about timing issues on the ESP8266, but is there no way to get rid of this? Do you think, upgrading to an ESP32 would solve this issue? Thank you!

Have a look at https://github.com/marcmerlin/FastLED_NeoMatrix/issues/6