Shoot, I was hoping to not have to answer this question, but I see there is still a lot of confusion.
First things first, just to get it out-of-the-way: the Samsung Wi-Fi mesh models do not in anyway extend the range of the Zigbee or zwave for your SmartThings account other than acting just like any other zigbee or Z wave device put in that physical location.
It is not True that each subhub gets to control its own set of the devices, the way, say, a secondary Z wave hub works on some other brands of home automation.
Instead, one and only one of your units will act as your home automation hub for the whole entire network. So you have to be able to reach that one in order to do anything with the zigbee or Z wave devices.
What the sub hubs can do is act just like any other Z wave or zigbee device on your network would act if placed in that physical location. Like a light switch. So they can repeat as long as they can reach one of the other devices of the same protocol which is closer to the main house. But they don’t do anything magical just because they are also Wi-Fi or because they are also a “hub.” They don’t add any additional range. They just repeat the same way a light switch of the same protocol would, but obviously with the advantage that you have both a zigbee and a zwave device in the same physical unit.
See the FAQ on this topic:
Automating an Outbuilding
There is an article in the community – created wiki on automating an outbuilding that should answer all these questions. So read that, and then if you still have any questions, just come back here and ask and we will be happy to answer. 
https://thingsthataresmart.wiki/index.php?title=How_to_Automate_an_Outbuilding
I’m going to ask other community members who do not fully understand how the Wi-Fi mesh systems work in a smartthings account to just refer people to the existing FAQs, and that will be the least confusing for everybody.