As per title, do I need to observe any specific specifications like transfer rates, SDHC vs SDXC, ultra, minimum read and write speeds etc? Maybe some companies are better than others? Any help most welcome. Thanks!
The one he linked to is a Class 10 card. That's about the fastest card you're going to see these days (and faster than the phone, so it'll be the phone that limits how fast the card can be accessed). I've seen mention of a Class 12 card, but it could be a typo or a rumor. It's not something for sale. (And no phone made could do anything with the extra speed - it would be like a Porsche in a traffic jam.)
Can you try mounting and unmounting the card from the storage menu?
Might also be worth formatting it in the phone as opposed to the PC? What File System did you use to format? Fat32? NTFS? The former is your best option.
Ah, ok. I misunderstood.
I'm not sure you can move apps TBH, with 16GB of storage, that should be ample space for apps etc?