WD Red 6TB using SMR omg?

[Stormy]

I have a Qnap NAS and two WD Red 6TB hard disks. Trying to decide between static/thick/thin. I know there is a performance hit but quite like the flexibility of thin as would setup three volumes with snapshot on one and over-provision. I can't get a handle on how much the performance hit might be.

Also I was horrified to find out my WD Reds are using SMR. As I will setup as a RAID1 I wondered if thin would be a problem with these drives versus static. Cheers...