Thanks for your reply.
Indeed sometimes I have some problems with German but mentioned literature charts are clear enough so far!!
Yes, either Forumslader and Dynamo Harvester Plus seem to be definitely superior when compared to e-werk/usb-werk.
It's curious to see that Zzing at 20 km/h seems to be the least performing.
Perhaps it's true, nevertheless I'm presently using one Zzing that I keep inside the handlebar bag and for supplying/keeping loaded both gps and mobile I think it works fine.
But hopefully one day I'll have the chance to test one Forumslader/Harvester Plus.