How fast can you cut?
Many people confuse laser cutting with knife cutting thinking that any size laser will cut any material at the top rated speed of a system. This is unfortunately not true. A laser uses a given amount energy to cut a particular material.
Like knife cutting, the faster you want to cut the more down pressure you need on the blade. The same is true with a laser, the faster you want to cut more laser power is required. The nice attribute is that the increase is fairly linear, meaning that if you are cutting a particular fabric, with a fairly simple design, using 50 watts of power and it is taking you 10 seconds to cut that design, then, using 100 watts of power would more than likely bring the time down to 5 seconds.

Can you cut multi layers?
Yes, most laser systems can cut multi-layers. But the question seems to be, is it practical? Using the same theory as the above question, when you cut 2 layers of fabric using a 50 watt laser, your cutting speed would double to 20 seconds. The only way to increase your though-put would be to cut 2 layers with double the laser power.