Nighthawk or Mesh for my house

Do you want to do it right and perform well but be expensive? 

Do you want to have a mesh system that's easy to use but has the same performance issues as the google?

Or do you want to cludge it together? 

Those are your options. 

Stone walls and thick walls do a great job of blocking wifi and are the bane of home wifi. 

To make homes work properly with those, you need to figure out a way to hardwire in access points around the home. The mesh systems with dedicated wifi backhauls (like googles) are going to struggle because they still use wifi to connect all the access points. So they struggle because their backhaul is sketchy. 

Options? If you want to do it right? 

Run ethernet throughout the home (or the rooms that need access points). Use that to connect the router/satellites up. You'll have better performance and the ability to upgrade easier in the future. If you have a hardwired backhaul like that you can use a system like the SXK30 or one of the lower end orbi/nighthawk systems as you don't need that dedicated 3rd band. 

If you can't run ethernet, if you're home is wired with coax, you can use moca adapters. Moca adapters are ethernet over coax. It works well and the 2.5g version of it has some pretty high throughput. 

there's also powerline adapters you can use. Older homes struggle a bit with these as their electrical systems tend to have more interference and impact performance/stability. But its an option. 

Or you can just use a mesh system like orbi and have lower speeds/stability if you're running off the wireless backhaul. It doesn't matter which system you get whether it be netgears/tplinks/googles as if they're using a wireless backhaul, they'll struggle with those stone walls. 

Or if you're cludging it together, you can get a router with extenders. Really don't recommend this system if you're needing more than 1 extender as they're not that stable with more than 1 extender. And it'll be worse in a home with thick stone walls. 

Me? I'd invest the extra money and run the ethernet wires. You'd be able to buy a little cheaper mesh system and have better performance throughout. But you do you.