if we have a right triangle with hypo x sqrt{2}, do the two other sides have to equal x?

If your right angled triangle is isosceles, i.e. 2 of the sides would be x, then and then only the hypotenuse will be x√2.

If your right angled triangle is scalene, i.e. all 3 sides have different length say (x, y, hypotenuse) then the hypotenuse would be √(x^2 + y^2). Try one thing here, if x = y, then it will become isosceles and the hypotenuse will again become x√2 !!