Can walking meditation be as effective as possible as sitting meditation?
Of course.
Meditation is not walking or sitting.
Meditation is the state of mind.
Sitting meditation has the added benefit of having fewer objects to focus on.
But walking meditation or meditation in any position can be equally effective.
The Buddha said, whatever yatha yatha va panitthang, something like that.
However the mind is, however you, whatever posture you put the mind in, be mindful of that.
So it doesn't matter what posture or what movement or what experience comes about.
can be effective.
Now, sitting meditation structurally is the most beneficial because there's very few objects to begin with.