FIRST, A NOTE ABOUT PRIMARY REGION FREQUENCIES
I know this isn’t what you’re asking, but I want to get it out-of-the-way first, because it’s the question most people ask.
The capability to switch between region frequencies was introduced in the 7th generation of zwave, series 700. You will find it on series 700 and series 800 hubs from companies like Hubitat.
Unfortunately, as of this posting all of the hub models that work with the Samsung SmartThings ™ home automation platform (which is what this forum is about) have series 500 chips, an older generation. They have their frequency set at the factory at the time of manufacture for the primary frequency for their intended region and it cannot be changed afterwards.
So…SmartThings-compatible models sold for North America Will be on that primary zwave frequency, 908.4
Models sold for the UK will be on that frequency, 868.4
Models sold for South Korea will be on that frequency 920.9
And so on. You can find specific model numbers on the Samsung website for that region.
Note that Zwave chose their frequencies by region in order not to interfere with local first responder communication devices. in some countries, it will be illegal to use a hub intended for a different region. It’s just something you’ll have to look into if you are buying an out of region model.
https://products.z-wavealliance.org/
So in the case of a SmartThings or “works with SmartThings“ Aeotec hub, it’s simple: each hub already comes region-locked to the frequency for its intended region and cannot be changed afterwards.
If you want a hub that does allow you to change the region, you need to buy one from a different company, which is using at least a series 700 chip, in which case it almost certainly has a Settings that allows you to change it.
You may already know this, but just to be sure, each Z wave hub can only work on one frequency at a time at the time of this posting and will only be able to communicate with end devices on exactly the same frequency. So you won’t be able to have some American zwave devices and some French zWave devices on the same zwave network communicating to the same hub. 
NOW, THE ADDITIONAL FREQUENCIES LISTED FOR A REGION
When A region lists more than one zwave frequency, the additional frequencies are implemented for higher bandwidth transmissions. The hub will handle that automatically. So you don’t have to worry about which one is being used at any one time: the hub will figure it out
This didn’t really become popular until series 700, so it just doesn’t typically come up in a smartthings implementation. You do see it on other systems, such as hubitat or homey, where once they went to series 700, you started to see more and more traffic at the higher bandwidth. It’s something like 2.4 versus 5 GHz in mobile phone communications. The newer becomes more popular once you have the hardware to support it, but the older is still used and it’s pretty much invisible to the customer. All the switching is handled automatically.
So on a SmartThings platform, you probably aren’t going to see much 916 usage. With a hub from a different brand, there may be quite a bit, but it will all happen automatically.
Select a certified Z wave hub based on the primary frequency for your region, and the frequencies used for higher bandwidth traffic, if any, Will be handled behind-the-scenes.
I hope that helps.
I rewrote this post since I first put it up because things have changed quite a bit with the series 700 Z wave hubs, and even though SmartThings doesn’t have one as of the time of this posting, I felt it was important to Explain what you might be reading elsewhere.