Removing post in center of two-car garage (20ft span)
Well, you could try one LVL and if it collapses, then rebuild the floor and use two.
It really depends on how much stuff you have in the room above and how solid you want the floor to be. Do you care if the floor bounces when you jump up and down?
I doubt that a 20 foot wall is not load bearing. What is holding up the roof? If you go into the attic, are there joists tied to the wall header?