Rapid tests can reliably tell if you are infectious, but they can miss early or late infections. So if using rapid tests as a prophylactic measure, test preferably day of the event, even right before the event if possible. As the chart shows you can quickly go from testing negative to testing positive.
In both cases, timing can affect the probability of false negatives. Too early after an exposure and you may test negative even though you are infected. So if you do know you had contact with an infected person wait ~5 days to test.
If you test positive with either, the false positive rate is low. So assume it is a true positive and isolate.