Ohio,
You need the pump to continusiouly run to provide hot water from the plate set up. A side arm will work off off convection and naturally move the hot water up.
Dirty,
My 50 plate is after my water tank and works fine. I have 1 1/4 horse sumbersable pump that moves my 55 degree well water...Water is hot

- but not so bad I worry about my kids getting scalled, they are older and know better - so no mixing valve. If I were doing this for others I would most likely go the Yoder route. Safer as the tank is a big fat hariy mixing valve.....