I'm not familiar with the machine you mentioned.
However ... when doing FMQ you do not use a walking foot. Instead she would use the Darning Foot or if the machine has it, a special FMQ foot. And yes, the feed dogs should be dropped for FMQ whereas they would be up when she is using a walking foot.
Stitch length is created acording to how she moves the quilt when she is working on it ... practice is what gets the evenness of the stitches