NEW Hub Replace Feature for SmartThings Hubs!

I currently have a V2 hub that does not have the built in TBR (Thread Border Router), unlike the SmartThings Station, the Smartthings V3 hub and the Aeotec hub. I would like to update to either the ST V3 or Aeotec hub, which I understand are essential the same hardware. I am currently using my V2 hub as a Matter controller. However, when I need to add matter a device, I must use my Gen 4 Echo as my TBR to add the device to my thread network and then get a Matter code from the Amazon app to be able to connect the matter device to my ST V2 hub. It would be easier to have a SmartThings or Aeotec hub with a built-in TBR to install Matter devices without going through the extra steps.

So here is my question based on the “Replace Feature” verbiage. If I replace my ST V2 hub with the ST V3 or the ST/Aeotec hub, what happens to my current V2 hub? Is it now a door stop or is it able to still operate as part of my location? If the latter is the case, with two functional hubs, do I have the ability to add devices beyond the 200 device maximum? Would I be able to use my V2 hub as backup at some point in the future to replace the ST V3 or Aeotec hub if they fail?