I sent an email to my insurance-company today to ask about these scenarios.
All of the above scenarios are covered in my insurance, no symptoms required. They even cover new flight-tickets if I can't catch my flight home because of the quarantine.
I'm covered if I tested positive when arriving.
I'm covered if I'm quarantined due to another person on my flight testing positive.
And I'm covered if I'm unlucky enough to catch if while I am here.
So I'm pretty much fully covered for covid-expenses on my travels.