I only use the method of dropping dechlorinator directly to the tank when I'm doing massive water changes (due to laziness and letting it go for too long once in a while.) Truthfully it's safe - but we don't know how safe. And it's not cost effective at all. Think about it; by treating your entire tank vs. only the new water you are basically wasting your dechlorinator because you have to treat for the entire volume, not just the new water. So say you're doing your weekly change - maybe 20% of a 100g tank. (Just to make the math easy.) That means you will literally use 5x the amount of dechlorinator that you actually need. And since you're dumping the water right in, there is the risk involved in too drastic a temperature or chemistry change which will stress the fish. There is no doubt that the fish will be getting hit with at least some chlorine, as it's not like the stuff immediately disappears the second it goes into the tank. It needs to come in contact with the added chemicals, and to dissipate at the surface before it is actually gone. I don't like that. I get uneasy when the fish swim into the current of the new rushing water from the hose.
Again, I have done the direct method many times without incident. But my preferred and usual method is the bucket on a stand. I have these old heavy duty studio montior stands that a friend gave me many years ago. I'll put a five gallon bucket on it, stand it next to the tank, and fill the bucket with my hose. This allows me to be sure my temperature is proper, and allows me to dechlorinate the new water in the bucket - saves me money and ensures that not a drop of chlorine gets anywhere near my system. I then run a siphon tube from the bucket to the tank. Nice and slow...gradual introduction of the new water. Far less stress on the fish. Maybe a bit time consuming as I have to refill the bucket a few times but I like the control, peace of mind and long term money savings that it offers.