Re MicroSD & 4K recording.
Class 10 is only the starting point to look for. Class 10/1 is vastly slower than a Class 10/3
So it's the second digit you want to pay attention too.
Some OEM's will label faster cards as x666 or X1000 with each being sequentially faster.
Re : the Amazon link posted.
Sandisk ULTRA has a maximum read speed of 90mb (in testing is often around 40-45) but a write speed averages only around 15-20mb. This is a Class 10/1 card and why it's substantially cheaper than Sandisks pro cards.
Sandisk Extreme Plus and Extreme Pro are the faster Class 10/3+ cards. With Extreme Pro being their fastest X1000 speed card.
You won't get the faster extreme pro or plus in 200gb but here's the 64gb version
http://www.amazon.com/gp/aw/d/B00NU...200_QL40&keywords=sandisk+extreme+pro+micro+s
These extreme plus and pro versions in my testing allow much more 4K recording without device overheating. Can shoot 3 times the length on my Z5 with one of the faster cards than with internal storage or slower micro SD. Likewise our professional Sony pro cams we only use x666 or x1000 (class 10/3) cards.