Best mobile data options for travel in DE and CZ? (bonus for DK and CH!)

I'm an American and I'd like to find out the mobile data plan options for a short trip to Europe this June 2016. I have an unlocked phone with solid worldwide frequency support and dual-sim capabilities (OnePlus 2). My plan is to leave my existing Tmobile USA sim in slotA (with Simple Choice 140 country slow-data roaming) and buy a chip, or chips, for slotB.

Primary goal is high speed data, I don't really care at all about voice or sms, but I'll pay a few bucks extra if those are easy to add on. I'll use my data carefully if I'm capped at a few gigabytes, but I'm planning to take photos and if I can get unlimited data (think 10gigs/day), I'll let my system continue it's automatic cloud backups while I'm roaming around. If I could pay USD$100 for 20gigs of data for a week, I would do it twice to cover my effective two weeks on the ground.

I'm landing in ZRH but only in CH for about an hour. I find airports are often the easiest place to get chips, but I don't really need connectivity for my time in Switzerland, so I can get a chip there or not (whichever is the smarter move is fine by me).

I'll spend the bulk of my time in Germany and Czech (almost exactly one week, if that matters I could literally get an "exactly 168 hour pass" for example).

I'll then fly to Denmark for 4 days, which might be an entirely separate situation where I'd also like to stay connected.

Tips? Tricks? Thanks!