Affirmations and manifestations ways can be different.
Affirmations are raising self energy. In the above link its requesting VK to manifest these affirmations into reality.
Manifestation is asking directly to Universe what we want.
If you use the lines as if you already have, you need to remain in that frequency for LOA.
If your frequency goes to a situation that you don’t believe it to happen to you, energy levels will drop, again you would need more energy.
When you manifest with I want….its easier to remain in this frequency, with VK you keep asking like a child.
Also a self motivated person may use "I want……
You can do the way you wish.
I personally feel asking to Universe directly to deliver what i want, is easier, without getting confused or doubting how to manifest or how to affirm.