2tbs here
I was most our clothes here with 2tbs Persil Megaperls (Universal or Color) + 1tbs STPP in our Bosch Nexxt 500 and everything comes out clean, fresh-smelling and stain free, in spite of the filth my 7 and 5-year-olds manage to inflict on their clothes. I do pre-treat ketchup and oil-on-cotton stains with a few drops of Persil Color Liquid and let those sit about 30 minutes before washing, but that's about the extent of my extra work. Occasionally I'll use 3-4tbs of Megaperls + 1tbs STPP for a load but that's only on really nasty kitchen/shop cloths that are being "profile washed" anyway, by themselves. I find if I use that much on regular loads (and especially towels) I end up with a lot of suds that are hard to wash out.
Now, all that being said I could probably get out all those stains without pretreating (at all) by upping the dosage, but since that leads to more suds with my washer I'm not convinced it is a good solution. Since literally everything else is coming clean with the 2tbs dose, I don't mind a little pretreating. Heck, the Color Liquid can even get out dried-in oil stains on t-shirts (that I missed the first time around) if I let them sit a few hours before I rewash. It is the best pre-treater I've ever used and has yet to fade a single thing.
Oh and our water here is hard as a rock. Lots of scale buildup on faucets, etc. that has to constantly be removed.