I have for the last 4 years a Schmidt Dynamo Hub, from Peter White actually. And a Toplink Brake pro plus. You won't feel any drag. Do they keep electrical items charged easily-depends on where you're cycling: prairies or mountains. In the mountains forgetaboutit. On the prairies, no problem.
IMO, a solar charger is a no go. Auxiliary Battery power is so easy to come by and charges items several times before they themselves need to be recharged. A dynamo needs to be constantly going at 12-14 mph. That is why it is not good at charging in the mountains. You'll charge going downhill, maybe but there is a lag before charging actually starts. Great for powering lights, maybe not the best choice for charging electronics.