Chlorine will disapate usualy within fifteen minutes but it should be left overnight as a precaution, this is more effective with air bubles. However there are many other toxins in your tap watter that won't disapate, notably chloramine, and metals. Following the intructions on the back of the watter treatment will remove most. When adding directly to the tank as the water treatment should be added with a dosage for the total tank volume. Some products will also require double amounts to remove chloramine read the instructions carefully this may not be clear. It would be advisabel to let your watter sit with treatment for at least fiuftenn minute though I myself add dwatter directly to tghe tank via python and add watter treatment to tank.
For priceing one of the best water treatments is seachem prime it should also work out the cheapest, (solid products are even cheaper but don't offer the variety of protection that solutions will) when purchaseing try to avoid products with aloe vera or "natural"components their effectiveness is limited and they rot in the tank
HTH