To cut 20mm Acrylic, you should use the machine with 100W laser tube made in RECI. In fact, 80W tube can cut it, but the cutting speed is rather low.
If your machine is used to engrave mainly, and do less cutting work, you can think about the machine with 80W laser tube, it can save you money.
Laser Cutting Machine CO2 Laser Cutting Machine High Speed Laser Cutting Machine