Step-up also offer a good quad workout, as they also bring strongly into play the hams (stretching the ham's) as well as the glutes. One of my favorite whole leg exercises.
Either stationary or walking lunges are exceptional movements, though a question of balance may arise, as well as foot placement, for the walking version as fatigue sets in. The walking version may need your undivided attention.
DJi81 is doing the Bulgarian squat (on foot resting on a bench, box, etc) which is a prime exercise. Well worth the effort to spend some quality time on these.
Just a personal view, but I don't hold much value to the whole knee over toe thing. Lot of Pro' & Con's from different trainers, of course..there always is for just about every exercise. Which can be good in a way. Find the exercise that fits your body type (muscle inserts, bone leverage, body leverage, etc). Find that a persons height (frame/bone length, as a given) can influence to how any exercise is preformed. A 5'6 man and a 6'2 man may need a different approach to some exercises, as Dl's & squats, as far as lifting style/technique goes. Good Luck.