What sensor type should my LX 400-800-810-900 printer be set to?
This depends entirely on how the label stock is formatted. See the simple graphic below for direction on which type of label stock requires which sensor.
Match what your label stock looks like to the graphic above and choose the sensor type indicated. The shape or size of the label does not matter as much as the relationship between the label and the liner. In almost all cases your sensor type should be set to Die-Cut!