Question

Can involve a tremendous amount of horizontal scrolling and require much zooming on small viewports

Answer 1

Fixed layouts can involve a tremendous amount of horizontal scrolling and need much zooming on small viewports. Fixed layouts do not alter in width based on the size of the viewport. Fixed layouts use fix dimension unit such as pixel to define the width of the extents of the wireframe that fix the width of the content irrespective of the size of the viewport.