The 7th ed VC codex covered the sunlight question fairly well. To quote, "One source of debate is how sensitive a Vampire is to sunlight. In truth, this varies with age and lineage. The sun weakens them, and may even kill lesser Vampires. The greatest Vampires can move abroad during daylight, though they do not favor it. To achieve its full power, such as in battle, a Vampire summons dark clouds to swathe the sky and swarms of bats to obsucre sunlight."