What is used for memory on the 4X? Hard drive? Thumb drive?
It is a built-in solid state drive. Traditional hard drive is optional. It has a place for inserting an internal SD card, and it reads USB drives. I haven't found a need for more memory.

I see the 4 X has pads(4) which look similar to the multipads on my Tyros. Do the function in the same way?
Yes, same way.

Text files for lyrics can be uploaded, correct?
Yes.

Tx

Rog L