Thumb's up Thomas.
Shawn, If all the NetGear APs act in Solo/Standalone fashion, you are needing to re-authenticate, re-dhcp, etc with every roam,
and the same would apply if you add any other brand Solo mode APs. This will not be friendly to streaming video/audio, xBox,
or IoT all over if you move around. If just for added coverage area, maybe.
If you run Unleashed code on the Ruckus APs, they would share client connection info for roaming handoffs. You would still
see the re-auth/re-dhcp renew if your client(s) roam between Ruckus and the NetGears. But check and see, can the Ruckus
R510s cover all three floors, if you turned off the R6700/R7000?
Running Unleashed on the Ruckus APs gives you Mesh capability too, if you have a garage/attic/basement that you can't wire.
Still some options you can consider...