Mounting a TV to Concrete Through Wood Paneling and Air Gap
I believe 3/4" is plenty thick enough to not need anchoring into the concrete. I've done this with plywood between studs without issue for mounting my tv and it is just over 40 lbs. The plywood was though thoroughly anchored to studs. Just ensure the best you can that the furring strips are well anchored and I think you are good to go.