na D5 to musi bezat pretoze tak je navrhnuta doska. Druhy pin (RX) nebude pouzity, bude sa len vysielat.
Co sa tyka rychlosti
https://www.arduino.cc/en/Reference/softwareSerial
The SoftwareSerial library has been developed to allow serial communication on other digital pins of the Arduino, using software to replicate the functionality (hence the name „SoftwareSerial“). It is possible to have multiple software serial ports with speeds up to 115200 bps.