Tides originate from the difference in gravitational pull between different sides of the ocean. If the Earth’s diameter were greater, opposite sides of Earth would be separated by a larger distance, and tides would be more extreme. If the Moon’s diameter were larger but its mass stayed the same, the tides on Earth would not change. The gravitational force between two bodies depends on their mass and the distance between their centers (i.e., between their respective centers of gravity). The moon's CG would not change location, so its effects on Earth tides would be identical.