Regarding racing while infected, came in contact with the case of a well trained athlete who during a track competition who went there feeling normal and without any symptom and almost fainted in the end of a run, something that never happened during the whole career (which spans for at least 12 years) and, according to the never, never felt so bad before (it was a 10/11 minute effort). That night did a test and came positive, despite having no symptoms.
So, being assymptomatic doesn't say much indeed regarding corona and physical exertion.