The ceramic diffusers have a pretty wide range when it comes to working pressure. Many of the atomizers, etc all need high pressure to work. I have them working from 20 to 60 working pressure. Whether you use a reactor, in-line atomizer, or in-tank diffuser they all work, evidenced by countless tanks, but sometimes one is better for someone else under certain circumstances.
Cleaning them is just 50/50 bleach/water dip for like an hour or more (that's why two comes in handy and if you eventually break one.)
I don't use powerheads, never found any "real" reason to do so. In the pic of my tank I attached there is a spray bar on the left glass above the diffuser angled slightly down that whips the bubbles around. The filter is just an Eheim 2215.