If cardiomyopathy was bad enough to cause low fevers, cp, breathlessness and palps, would it show a sign like increased inflammatory markers, a murmur, low o2, weird bp and/or ekg changes?

Yes: You have listed most of the common signs.

Many forms; depends : Cardiomyopathy is a big word that means poor heart function. There are many forms of cardiomyopathies, and depending on which one you have, there are different signs and some are reversible. Hypertrophic cardiomyopathy: enlarged heart with ekg ; echo changes; viral cardiomyopathy: prodrome of viral syndrome which results in cardiomyopathy ; 50% improve; and many others. Discuss with your doctor.

General vs specific.: Keep in mind that cardiomyopathy is a general term describing a change in the muscle of the heart. Thickening, thinning, weakening, stiffening, etc. What causes low grade fever and elevated inflammatory markers would be something like myocarditis, pericarditis, or endocarditis. "Itis" means inflammation. So fever, elevated inflammatory markers are associated with autoimmune or infectious origins.