X-ray shows borderline enlarged heart, with slight curvature of spine. My heart echo looked good with rest HR 58-68, EF was 64-71. Should I be concern?

Echo Results. I would certainly discuss your concerns with the physician who ordered the tests, that is always the best policy as he/she knows the whole clinical picture. The numbers you gave are normal, however you did not comment on the valves or other cardiac architecture which is important as well.
Borderline. The heart size by chest xray is very often inaccurate. Your echocardiogram would give accurate heart chamber dimensions and, I assume they were normal as you haven't mentioned otherwise. Your left ventricular ejection fraction shows no evidence of cardiomyopathy either. Coupled with no history of systemic hypertension or valvular heart abnormalities, there should be no reason for an enlarged heart.
The xray. finding was likely spurious, a chest xray is not the most accurate way to evaluate heart size unless it is grossly abnormal. A "borderline" enlarged heart on chest xray is usually normal, which was confirmed on your echo.