SoftwareSerial with ATTiny84 using ATtiny library

That worked right out of the box !

So it seems that if you only need the output from the tiny you would choose KnockBang, and if you need to also send something to the tiny you would use
RelaySerial ?

Another observation in the test script you use

 Debug.begin( 250000 );

But you have to set the serial monitor to 19200 (I mean usually they should be the same) ?