If you want to roleplay guiding bolt effectively, then you need to look at the god your character worships. All holy magic is representative of the god that your character worships. If your character follows Moradin, the good of dwarven battle and honor, perhaps your guiding bolt could be a mystical hammer that flies towards the target and showers them in light. If your character follows Auril, the goddess of winter, the guiding bolt could be a beam of frost that covers the affected character in a thin sheen of frost. Plus, if you upcast the spells using a different spell slot, don’t just say ‘I’m casting Guiding Bolt at 3rd level’ instead describe how the beam of frost is much colder and thicker and usual, or the mythical hammer is much much bigger. It’s mostly for flavor, but it can be a lot of fun to customize your spells visually and make them all about your god. The customization and making every single character different is what makes 5e D&D so much fun. Plus, it allows others to RP as well and makes D&D (and especially combat) something that you can make a story about rather than breaking away from the story to roll some dice. Not every player will want to do that, but if you have a group that focuses on storytelling, it can be fun for combat.