Under normal circumstances anything that is highlighted as under investigation after the race will not result in a penalty that changes that race result. It will be things like grid penalties for the next race.
The exceptions are incidents that happen in the last few laps of a race where the stewards don't have time to react, or incidents that were not identified during the race but were raised after it that would have received an in race penalty had they been raised during the race.
The exceptions are incidents that happen in the last few laps of a race where the stewards don't have time to react, or incidents that were not identified during the race but were raised after it that would have received an in race penalty had they been raised during the race.