I donlt actively fish, so can't answer with respect to finding something to catch, however I do suffer from a cronically small console, so don't have space for a full blown fishfinder.
Personally, I just need to know how much water is (or isn't !) under the keel, so a digital display suffices. The "numbers only" ones come in all shapes & sizes from something the size of your battey level meter to 4" digits (for racing yachts so you can see it from anywhere at a glance) Someone (Raymarine?) does one which has a "trendometer" at the side so you can see at a glance how quickly the numbers are going up or down, something you would see with a graphic fishfinder anyway.
If you already have a plotter, you may be able to get a relatively cheap NMEA2K sender, & get a digital readout on screen. (depends on the plotter) I think Lowrance or teleflex, I can't remember which ) also does an NMEA2K digi dial which you can program to display pretty much any data avaialble on your network. Also means you can use it for other NMEA stuff as well.
As a tip, if you want to find the "numbers only" ones, you are usually better googling "echo sounder" than "fishfinder".