Sorry i haven't replied to anyone. I was called out of town for a bit.
I am using all the topps apps
Huddle, Bunt, Skate, Star Wars, Marvel, Walking Dead, Kick and Slam
Although currently I am only active on Huddle, Bunt, SW and Marvel. I don't have a lot of space on my Samsung J3 so I can't keep all of them installed but my accounts are there if you ever see something you want to trade for on any of them it's easiest to get ahold of me on Huddle.
As far as Panini goes I only use Blitz, I had the Basketball one (Dunk I think) but deleted it the first day I had it.
As for collecting Digital cards. Well The way I look at it is if they sell on eBay it's worth looking into. Some people are making a little money with them. Its just kinda risky, if Topps ever stopps support for the apps you'll lose your collection. That is why I haven't spent any real money on the only the free credits you get in the apps.
Trying to put the sets together is still kinda fun though and plenty of people to trade with. I kinda wish Topps would do some sort of Auction feature like Panini has. Panini is ok but the community is alot smaller.
Well I rambled enough so I'm outta here, Check me out on all th Topps Apps (TheTexasRaven)