With my one full day in Reykjavik pre-cruise, I've booked a South Coast tour. Jokulsarlon glacier lagoon and Diamond Beach look more dramatic (and maybe less touristy?) to me than the Golden Circle stops, but now I'm second-guessing. Will I be missing out on the best/most iconic sights by forgoing the Golden Circle? Planning to do Blue Lagoon and explore Reykjavik the day before.