Hi
The gravel is not like Unbound gravel. This gravel was ground by glaciers so much of it is round and without sharp edges. You will also encounter quite a lot of “volcanic gravel” which is sharper in nature. Ted King takes a look at this here: King of the Ride: The Rift, Iceland's Stunning Gravel Race - YouTube.
That being said, I will be carrying a patchkit and a tube along with my tubeless plug repair kit. I really don’t want to be stuck out there in the middle of nowhere. It’s very remote.