What can I do with HotSwap Bays

I am planning to upgrade my NAS soon. I want to install (among other things) a HotSwap bay for desktop hard drives. I was thinking along the lines of this but I’m starting to have second thoughts. I know how I can just plug in a USB drive somewhere and the system will just make it available, but a hard drive isn’t USB. Which brings me to my questions.

  1. Will these bays allow me to swap out drives like a USB drive while the system is running? I think the buttons on the right of the bays suggest (at least to me) that I can switch the power on/off of the bay slots to safely swap them out (as detailed in this video), but i’m not sure, and I don’t want to “dive in the deep end only to find out that the pool is empty.”
  2. Do I have to use “special” hard drives or can I use any drive I might have on hand (assuming its sata)?
  3. The one I used as an example is just an example. I want one with at least 3 bays. Does anyone have any suggestions/objections?