always use HE powders (Tide, Gain, or Persil)
I mostly use domestic HE powders, Tide or Gain. For my work clothing (khaki trousers and button down shirts, either pastel or plaid or dark solid), I use European powders I bring back on trips: German Persil, or Unilever's Persil from other countries (UK Persil, Omo, Via, etc.).
My work clothing is rarely heavily soiled. In my 3.5 cu ft Frigidaire 2140, I use 2 tbsp per load. I just use a steel coffee measure (30 ml or 2 tbsp). Most of my work clothes are 100% cotton with wrinkle free finish from LL Bean, and I run them on a Perm Press cycle for both washing and drying. These loads dry in about 30 mins (including cool down phase of drying); if I use a regular wash cycle with longer/faster final spin, drying time is reduced by 5-10 minutes, but clothes don't look as nice (more likely to cause wrinkles during final spin)
For towels and sturdy cottons, I don't waste my European detergent and just use 2-3 tbsp of Gain or Tide HE powder. Both work fine.
In general, my amounts are about half of what are recommended on the box (including the European boxes) and everything comes out clean. I have hard water and no water softener. I do generally add some Borax to each load, which I am told acts somewhat like a water softener. What I have noticed is that detergent seems to rinse out of clothes better if Borax is added to the wash cycle. Without Borax, I tend to see more suds on the door and gasket. Borax is very cheap here, like $4 for a large box. My clothes seem to last a long time, so I would imagine that Borax isn't harmful to clothing longevity.