MT-10 Genuine Panniers and 59L Top Case

I have the 59L top case and mostly head off on weekends with my wife on the back of the bike.
I'm looking at additional storage for our trips and whilst a tank bag appears to be the cheapest option, I've never used one before ? and I'm left wondering how much damage a tank bag could do to the matt black finish of my MT-10 tank.

So in looking at the genuine Yamaha soft side case set (panniers) I read that Yamaha themselves do not recommend using these at the same time as the top case. Anyone know why?

Also this, Panniers "Cannot be mounted with optional Akrapovic exhuast." - I assume this refers to the link pipe, removal of the cat and addition of the Akro can and not simplythe akro slip-on ? I have the graves slip on and cat still installed.

Any info/advice appreciated.