We have a 130W ShenHui CO2 laser cutter. It cuts leather, cloth, wool, fur, acrylic, wood, and other non-metal materials. The bed is roughly 4 ft wide by 3 ft deep.
We use RDWorks as the software for controlling the laser. The general workflow is to draw something in a program like Inkscape or FreeCAD, save the drawing as a dxf file, then import the dxf file into RDWorks. RDWorks is then used to control power, speed, and cutting operations before sending the job to the laser cutter.
RDWorks is setup to read dxf files in units of inches, so make sure to select inches when exporting from your design program. Otherwise, the size of your part will likely be wrong.
If your parts are dimensionally inaccurate (i.e. circles are coming out as ovals), there's likely something wrong with the drive belts, probably tension.