I use the fast 64 Gb card.
According to my type of filming 128Gb is probably too much as I have never filled up 64Gb in one day.
And maybe for safety measure if it is lost or broken you'll have less loss of the filmed material.
I bought one recently and I know the symbol for the V10, but there's a number 1 inside a large "U" looking thing. Is that the UHD number? I just Googled it and found "UHS" numbers. Is this different or are we looking at a typo here?