...I have attached the scheme, will it work?
How will 5m pieces fit on a 2m wall?
probably understood, but just for completeness sake, the 2nd GND for the 2nd row is not there, and neither the DIN-DOUT line.
What arduino would be better to use for it Mega or Due? I guessed to use Due because it is a bit faster, but conversion 3.3v to 5v looks tricky.
...still need a logic level shifter (e.g. 74hc14)....
Those bi-directional modules are designed for i2c, which is normally 100KHz or maybe 400KHz. NeoPixel signals are 800KHz....But using 74hc14 for i2c level conversion would not work of course because a bi-directional shifter is needed.
...The Schmitt trigger is not necessary, a basic 74HCT04 is just fine, but it is always a "nice" idea to "sharpen up" the waveform using the Schmitt trigger....