Hi it's Illi,
I'm no pro but I can say that it is whatever you feel most comfortable with... To each their own.
I use an 8,1 accell, zero dead zones... But that is only bc I used to use a 10 and found it too fast.
I do recommend the 8 bc it gives a looser feel that works with the aim assist. I'd give it time but 7 seems to be fighting against the aim assist.
Nevertheless, whatever feels right to you.