1.) this would be more STRIP related than 'MATRIX/CUBE'.... (for the project/demo).. does that matter? same principle applies?
No, it is the same it dosn't matter how you physically arrange the LEDs.
I didnt see any mention of shift registers?
They are just one way of getting extra outputs, they are not essential.
1 I/O pin per 2 leds doesnt seem very 'convenient??
Sorry don't know what you are on about here.
what if the LEDS used need/require more than only 8mA?
You use LED drivers, direct connection to a shift register is a bit babyish.