Ref hot swap. UnRaid itself does not support hot swapping. That is to say that, if a drive fails, you'd still have to power down the server to replace it. It just makes it a bit easier to change/add a drive should you need to. So, if money isn't an issue, then go for hot swap. If you want to keep the cost down, then don't.
i think i will start without the cages, and see if it disturbs me like that...
but one other question about it
if i use such 4in3 hot swaps, do i need to connect each harddrive with power supply or do i connect only that cage with power supply
so in other words: using hot swaps makes less use of cables which means more ventilation or not?