Does anyone here have A laser cutter with the Z-axis bed?

Does anyone here have A laser cutter with the Z-axis bed?
I was wondering if the feature would be very helpful, as the focal point on my k40 is constant. Do the lasers with Z-axis beds have any means to adjust the focal point as well? Or is that all manual?

on my laser I just removed the stock bed entirely, and installer rails on springs,
I push the rails down and adjust them manually, its pretty simple. where there are only 2 rails, I can also fit items in and prop them up with different size blocks to hit my focal point. Im just wondering if Z-axis control offers a worthwhile improvement to my laser use.

I have a powered Z axis and I would say that a powered Zaxis is a convenience over what you are doing now. Sometimes it is a pain to find the right spacer (block) for different materials. Exact focus is important for quality.
I use my a lot.

My table: Don's Laser Cutter Things: Stand alone K40 Zaxis Table & Controller Build

There is also a clamping design out there that sounds like your rails.

I did this design but never built it:

What is the focal distance from the the lens to the surface material being cut or etched?