"Mike" wrote in message
My questions:
1) Is it okay to just turn off the water supply and water heater
without releasing the pressure?

Yes.
You should also turn off the water heat. The chances of it running dry are
very low, but why take the chance?

As for opeing a valve, ther eis very little pressure to let go. If you were
to open and close it the pressure would be eliminated in seconds and the
water still left in the lines. IMO, it does not matter.