

Only when you have to write out to swap. In the case of something like ZFS, it stores data in RAM, looks for it there, then looks on the disk. So freeing up the RAM is effectively instantaneous; you just mark the space as free, then the other process writes into it.
I do, but it’s more out of laziness than anything else. I hate having to remember sixteen different ways of doing things, so I tend to configure all my stuff as identical as reasonably possible. Is this the best way of doing things? Probably not. But it keeps my blood pressure down.