Might as well throw my experience up. I've got a Garmin 1000, iphone, front and rear Niterider lights with internal rechargeable batteries on my touring bike, with a Son28 front hub, Sinewave Revolution converter, and a standard USB power pack. I run the Garmin 100% of the time and poke at the phone a lot for navigation and photos. Lights aren't for night - but for inattentive stupid and texting drivers using strobe modes when I feel it necessary (I noticed an immediate decline in attempted murder by Uber drivers on my San Francisco commute when I did).

The battery pack has a charge-through capability, though when I plug the hub into the battery pack and other devices into the pack, nothing actually gains charge, just holds more or less steady. Must be some efficiency loss in the pass-through, because anything I plug directly into the converter gains charge steadily. So I mainly charge the Garmin until it gets 100%, switch to charging the phone until it's adequate (going to airplane mode and/or turning off Bluetooth and wifi speeds it up a lot), top up the powerpack, back and forth as needed. I usually unplug from the converter on climbs, as below ~8mph it doesn't produce enough power to charge anything, but the drag is unquestionably noticeable. The lights, I tend to charge from the powerpack at the campground (or a wall outlet when such luxury is available).

At the moment I'm starting to build a waterproof switch circuit that lets me switch from off, to Garmin, to two other USB outs to consolidate and simplify the works. And before you tell me to simplify by throwing it all out - save your breath.