There's so far no differences between "standard" myocarditis and covid-vaccine induced myocarditis. Heart damage is heart damage. Inflammation is inflammation. The heart takes a very long time to regenerate, if at all, because it is constantly in use, contrary to any other muscles that can rest. That's why myocarditis is always bad, no matter how mild it is, because it's almost always permanent damage.

Until long term studies are done to spot any difference, we can only assume myocarditis are the same for now in both cases. Oh, but wait, so far, there's no studies in effect, because "There's no vaccine side effect, and if you dare say otherwise, we will cancel you everywhere and revoke your license". So yeah, good luck proving anything.