No, the amount of drift is similar whether spraying concentrate or dilute for correctly set up airblast sprayers. If the helicopter rigs are well set up and operated they can be efficient at spraying the target area. Measurements of drift from helicopter spraying showed only low levels of drift, no higher than from typical ground spraying. However the potential for serious drift is much greater if there are high winds or there are errors in the targetting of the spray. No, significant contamination of tank water from roofs used to gather rainwater is unlikely, especially for buildings well away from the boundary.
Some sprays contain impurities in their formulations which smell unpleasant but have a low toxicity.
The smell of spray does not necessarily indicate significant drift of pesticide is occurring. The trials by Holland, Maber and their team showed that somewhat higher levels of drift were recorded from spraying apple orchards compared to kiwifruit. This may be due to site and climate as well as apples having a less dense canopy. The need to project spray further to cover the taller crop may also be a factor. Spraying equipment and shelter, rather than the crop itself, will also influence the degree of drift.