Hi, I am getting a new kitchen and we ripped out the old one .. I measured and base unit height with Worktop was 35.43 inches and same for new units coming in. I am sure a little more or less shouldn't be a problem .. It just make working on the counter harder if they are higher, if you are vertically challenged ( like me).

Standard is 36" including the top. The opening for the dishwasher should be 34.5" tall. If you have a slide in range, the tolerance is not very much, so look up the heights on the range installation instructions. Why do you want 3/4 plywood underneath. I can think of a few reasons you might think this is a good idea, but none that are necessary if you are not putting anything over the remainder of the floor.

Just make sure that you measure correctly to then mount your wall cabinets. Need 18" from countertop to bottom of cabinets (generally).