Are higher-dimensional beings infinitely larger than lower-dimensional equivalents?
In a way, yes, though not how most would think when using this word. Basically, an arbitrary object of dimension n is essentially comprised by the total sum of uncountably infinite objects of one dimension less, which may be described as lower-dimensional "slices", each corresponding to one of the infinite points of a line. For instance, a square is made of infinitely many line segments (Lined up on the y-axis), a cube of infinitely many squares (Lined up on the z-axis), and so on.
One may think of it as a multiplication between sets: For instance, the unit square [0,1]² may be expressed as the product of two unit intervals [0,1] x [0,1], which itself can be visualized as taking "copies" of the first interval and lining them up along each point of the second interval, of which there are uncountably infinitely-many, thus forming a square out of infinite line segments.