Add Isilon nodes with newer version?

So we have a cluster with 4 H500 nodes running 8.2.2.

Now we've bought 4 new A200 nodes and connected them to the backend switches.

In the webgui under "add node" they show up running 9.1.

Now what would happen if I'd actually click "add"?

Would they be downgraded to 8.2.2, or just added with 9.1 as is? Or would it fail? 

Can't find anything in the documentation referencing this situation.

Ps. We've also bought a smart pools license, and I figure I need to activate it and set the default node pool target to the H500s before I add the A200s, or else it'll start writing stuff to the A200s as soon as I add them, correct?