Yes, class 10 is currently your only option. You should basically buy a Samsung EVO+. Even then, performance will not be very good.
That being said, there is a new type of sdcard coming soon, the UHS-I A1 type card. They are actually meant for running apps off the sdcard.
How bad is not very good?
is it still slower than internal memory?
Does this devices support UHS/Class 10 SD CARD?
at this point I already have too much MicroSD, because every phone I bought always includes it (2GB-32GB)
I was actually just recently start to using this phone again after reading various websites, I always love it, it small, compact.
The reason why I stop using it is because the internal memory is pain in the a$$, I can't update anything because it's full and can't use it either because everything needs to be updated, with custom rom it's doable.
I've used CM13, but it's too slow, so I downgrade to CM10, but the Bluetooth doesn't works, not big deal actually but it's basic feature.
I'm running CM11 for now, it's pretty fast, everything works perfectly but the problem is always the internal storage.
Even-though I've already set External storage for default storage with ADB commands, the system still using internal storage for cache and installation which always getting error because 100MB can't store anything beyond that (for example: whatsapp alone required more than 50MB+ for install file)
I don't game on phone so idc about games.