There are certainly plenty of wasp/hornet sprays that require you to be able to see the nest or insect to spray it, and I keep them around for red wasps, and paper hornets. Some of them are absolutely great sprays and kill pretty much on contact, and work very well for the wasps/hornets you can actually see. The problem is, if you can't see what you're spraying, it's going to be hard to make that contact. Most insecticides are contact poisons and AFIK, NONE are aromatic/fumigates anymore. Most Aromatic/Fumigate insecticides are proven EXTREMELY dangerous to humans/animals. Yellow jackets don't play by the rules that wasp spray manufacturers want them to, and rarely build their nests so that it's easy to wipe out the colony with feel-good green friendly techniques. I play their game when needed and one-up them. They have no other intent than to kill or harm me when they attack me, and all I was trying to do is cut weeds and poisonous plants so I can enjoy my property more. They don't pay part of the mortgage, so their choice is to live by my rules and not sting me or suffer the consequences. I just reciprocate with more intelligence and better tools and materials. I don't react that way to all stinging critters. I found a nest of ground dwelling bumblebees this year (the hard way). I just let them be until this winter when I'll remove the debris they're nested under. I try not to kill pollinators.
Never mind that my yard was most likely the city dump before its purpose was consolidated with the county landfill, and it is full of voids and stump holes that the developer was NOT required to fill in. There are voids in my yard that are large enough for foxes to den in, which are also prime locations for jackets to build. I assure you, this yard is a lot cleaner since I've been here than it was when I bought it in 2004, and certainly than it was before the house was built in 1975. I could go on for pages about the things I've dug up in this yard. The half pint or so of gasoline I've used for killing yellow jackets since 2004 would be an improvement. If soil poisoning is going to happen, someone's beat me to it. I promise, I use my technique sparingly and with the least amount of gasoline that I think will kill the nest. On occasion, it may take two applications because I underestimated the size of the nest and don't get 'em all. I sprayed one with Raid wasp/hornet spray this year, and killed all the vegetation within 5 feet of the hole. I've never seen my technique with gasoline do that. I've even killed a nest under an azalea bush I planted. The bush is very much alive and healthy. So we'll have to agree to disagree that the commercial products are better because the quantity required and the vehicle and propellants used in most of them are worse than gasoline. Neither is actually good for the environment, but neither is a buried human body full of formaldehyde because a wasp sting put them there. As far as I know, none of those are on my property, but I won't be surprised if I find one. Ask your favorite exterminator about killing yellow jacket nests. They REALLY hate doing it because it's so hard to do. My step-son worked as an exterminator for a while, which is how he found out he's allergic to wasp/hornet stings. It shortened his exterminator career significantly when he filed a worker's comp case for his hospital stay.
Gentlest wasps? I gotta think on that one for a minute. Sounds like an oxymoron to me. Maybe they're different on the east coast because they're certainly not friendly down here. Maybe we just have bigger, badder cicadas that put up a better fight, or the heat/humidity does something to them. We have a few bees that are not aggressive, but I can't think of anything in the wasp/hornet family in the South that fits the description of "gentle". Maybe a dirt/mud dauber, but even those have their limits.