The expeditions are available as PDFs and can be played anywhere, although frankly they aren't really anything to get excited about. Each of them are smaller and less detailed than a single adventure published in Dungeon. There have always been minor rewards available to folks who participated in the Wednesday night encounters program. Back in the 4e days they gave out free Fortune Cards. From what I've seen, there really isn't anything 'extra' included for HotDQ as far as loot or in-game items for the participants, but there might be something in the actual in-store packets that is missing from the PDFs available on the encounters site, I'm not sure. Also, the encounters version of HotDQ only goes through Episode 3, and although you can continue playing it beyond that if you have access to the hardback, there is no support in regards to AL rewards if you do so.
In other words, while I do think that WotC has provided a nice framework for in-store play, there is nothing that I've seen to lead me to believe that the in-store experience is somehow given preferential treatment over the at-home experience. I certainly don't consider the very minor rewards of faction pins etc to be an incentive to play in-store.
As far as digital editions of Dungeon and Dragon magazines, I maintained my subscription to DDI for years after I stopped playing 4e, simply to have access to those two online magazines. While there wasn't a lot of content I could use in my earlier edition games, I still found there to be enough articles and adventure seed ideas to make the subscriptions worthwhile. When they stopped distributing Dungeon and Dragon I cancelled my subscription (it runs out this month...) but if they were to bring the magazines back in digital form, I'd re-subscribe in a heartbeat. Those two magazines are a great source of material regardless of the edition.