Dynamo hub in 700c wheel for charging at low speed

andyh01 Posts: 599
Hi all
I'm seeking advice as looking to go to a dynamo hub mainly to run lights particularly daytime running lights on a relatively short commute. I would also like to charge devices like GPS computer or phone either while commuting if got a low battery or when out on longer rides.
Anyway the bike has 12' thru axel with 700c wheels so I was looking at the Son delux; my research suggests this was designed to go into smaller 20' wheel so while the drag is reduced so to is the efficiency and it's recommended to use the Son 28 hub especially when travelling at slower speed?
Anyone had experience of charging devices and running lights on the Son delux hub -what average speed do you have to do to get the catch batteries to charge and in turn charge the device?Any real world comparisons between the two hubs in the bigger wheel? Could I get the Son 28 hub (15mm thru axel) to fit my 12mm thru axel frame?
Thanks Andy