Its the same mechanics for a rain team its just that politoed has drizzle which makes a peramnent rain that can only be messed by pokemon like t-tar or ninetales or pokemon with the moves sunny day or sandstorm and than theres this vaporeons ability which makes it so it wakes up automatically in the rain so that you can exploit rest when need be
Also, you wouldnt need to do 5th gen if you didnt want its just an option in the simulator... You should download it still though its great for testing teams before you actaully go and have them fully trained and bred and what not.