I use my Lx-3, which does not have the SFL feature, and i use it as long as the depth is 3 feet or more. I use it a lot in 3-5 feet, because most of my local haunts aren’t much more than 8 feet, with 4-5 feet being the norm. Any less than 3 fow, your jig won’t hardly show up because the cone is so tiny. Most of the time i am fishing that shallow, i can site fish anyway. Flashers rule! And to answer the last question, yes the marcums have a split screen zoom view…The left half is the zoomed 5 or 10 foot range which can be adjusted to kee in on anywhere in the water collum, and the right side of the screen is the entire water collum. The zoom feature is an awesome feature to have, especially in weedy areas or in tight schools of fish because you can actually see the seperation on them. I have never used the lx-5 but i am sure it is 10 times better