Replace RT-AC87U w/ pair of AC86U in AiMesh?

So I'm thinking of picking up a pair of RT-AC86U routers to replace a flakey RT-AC87U I have now if it will fix my dead spots. My current router is located at one end of the 1st floor of the house, and my son is constantly complaining of bad wifi on the OTHER end of the house, 2nd floor. I was thinking of replacing the current router with a new 86U, and then either...

1. Putting the other RT-AC86U upstairs on the 2nd floor, somewhere possibly centrally located, which would need to...

Replace RT-AC87U w/ pair of AC86U in AiMesh?