I'm new to SAGA.
I've got a srtm data set from europe and want to charge the maximum flow length especially from the river Elbe. The data is in WGS84 So first I ran the tool "Fill Sinks"(Wang & Liu) and the flow length downstream but the output flow length were in degree. So I transformed my original data in another coordinate system (I've tried EPSG 4087, 32662 and 54031) with meters as unit and ran the same tools but the watersheds and the flow length looks really creepy in those cases.
Also I have no clue what the "maximum slope legth" in the "Fill sinks" tool stands for.