Do you know if it's possible to create layered sounds with tyros 5 using YEM and internal voice elements ?
Yes.
Is it possible to affect each element to specific velocity ranges ?
Yes.
YEM Owner's Manual, bottom of page 16 and top of page 17. Please also look at the screenshot on Page 12. You'll see little squares at the top, bottom, left and right on each waveform box. Drag the left and right squares to change the key range. Drag the top and bottom squares to change the upper and lower velocity limits.
I assign each layer to a separate element. This makes it easy to manage the voice design when there are many waveforms in each layer.
Hope this helps -- pj