The pressure will not change by reducing or enlarging the diameter of the pipe. What will change is the volume or flow. The pressure is predetermined by the pressure in the city water main. If that happens to be too high, it can be run through a pressure regulator valve and lowered, but if it is too low, you're stuck with it. One problem with using 3/4" inside the house is with hot water. The entire 3/4" pipe between the water heater and the hot water faucet has to be purged of cold water, and a 3/4" pipe has a lot more water in it than a 1/2" pipe. This wastes water and takes time. Of course, you could install a recirculating pump which requires a return line. That would give you instant hot water. For the fixtures you describe, I believe 1/2" inside the house would be quite enough.