I've got a question:

Let's say I submitted four LORs for a school which requires only two LORs. Do you think they all will be read by the committee? Or do you think more than two LORs may be a disadvantage for an application?
I have no any experience about that.
Opinions please...

Why don't you let the school know and ask them what to do about it? If anything, having 4 letters of recommendation will probably not help you, since it demonstrates to them that you don't follow the directions that closely.