Sun / Moon Set >>?

The daily motion of the Sun and Moon are of course illusions caused by the rotation of the Earth. These motions are always parallel to the equator. The horizon is perpendicular to the equator only if you are at the equator. So you are right when you suggest that the rising and setting would always be perpendicular to the horizon at the equator. The angle of the path of the setting Sun is not related to the axial tilt, only your location on Earth. But the point along the horizon where it finally sets does depend on the axial tilt. If the axis were not tilted, the Sun would always set due west. It would approach that due west point at 90 degrees if you were at the equator, and it would approach that point at an angle equal to 90 minus your latitude if you were not at the equator. At the pole, which is 90 degrees latitude, the Sun would just sit on the horizon all the time, but go around you, just at the horizon, once a day, never rising or setting. Its motion would be parallel to the horizon. This can be seen in reality on the day of an equinox at either pole. If the Earth's axis were not tilted, everyday would be an equinox day, because the Sun would always be on the celestial equator.