So my question : are agitator/impeller toploaders able to cl
Yes, provided one knows what one is doing.
Just means thinking a little backward instead of modern way.
Have washed everything from badly soiled kitchen linens, to white socks worn indoors as slippers so long they ranged from grey to "yuck", and everything comes out whiter than white.
Top loading washing machines by their nature have more to do with the old "dolly stick" washing of yesterday and the "pounding on a rock" action mimiced by front loaders.
To clean badly stained laundry properly in a top loader, one needs to do women did years ago; first a warm or cool wash soak, followed by a hot wash, all with proper detergents/soaps.
The cool to warm pre-wash or pre-soak carries off a major part of the dirt, loosens soils and stains, and also prevents same from being set by hot water. The hot wash shifts whatever soils and stains are left.
As for bleaching in a top loader, most use LCB, but one or two washes (as in pre-soak or pre-wash, then main wash), with a good detergent containing advanced oxygen bleaching system (such as Tide with Bleach), will shift even the most stubborn stains. Indeed a very good enzyme detergent alone, without bleaches of any sort can and will shift most stains,especially if given enough time to do the job.
Certain stains are always pre-treated regardless how I am doing the wash, top or front load or twin tub. Blood stains will shift easily without bleach if they are pre-treated with a good enzyme based stain product. Old and or set in blood stains may require spot treatment first with enzyme product then oxygen bleach, either way they are gone.
Problem with top loading washing machine results, lies not as much with the design of the washer, but how most do their laundry in the things.
Bunging in a load of clothing, setting the machine to "hot" and hoping for the best. simply will not do.
As for front loading washing machines being more gentle on wash than top loaders; well yes that was true when the former actually used more than a cup full of water to wash clothes. By and large today most machines barely wet the load down and to compenstate for decreased water use, have exteneded wash cycles. So now you have laundry being beaten about itself and against the wash tub for almost an hour in some cases, just for the "wash" cycle. Enough of that often enough and you will have badly worn items.