Thanks for bringing me to this thread Barry. LMTD has the gist of the chemical side.
I was deeply disturbed to read 20% of someone’s mix was surfactant. Pretty sure that will take 10 hours to rinse off or attract dirt from even 5 miles away, lol! For a regular glass cleaner if I put in more than 0.2% of a surfactant it will leave streaks behind. You want to break the surface tension, not cover the house in foam.
I think the term surfactant is used too broadly on this site, as in anything that bubbles is a surfactant, and it isn’t. Soap has surfactant in it but is not itself a surfactant anymore than my moms brandy cheesecake is an alcoholic beverage 
It’s fair to ask what percentage of SH should hit the house. I tell people around 0.5% when they call. If your machine puts out 1:10 then you have to dilute the SH first, 1:20 is more common, but I’ve gotten calls from people asking about 1:5, so they are out there too.
This all boils down to personal preference of mixes, equipment, “soap” choice, and what you have staring you in the face at your job. Is it a house in the shade that looks green or is it a concrete walkway that just looks dirty? Everything is subjective to what you are dealing with at each job.
Now I’m going to cook a soup for my daughter, y’all behave 
P.S. I use oxalic often for rust remover and deck washes to calm the tannins in the wood down after caustic cleaners or strippers are used. It’s a great acid.
