So long as your iPad isn't so old, you can just Airdrop between an iPhone and iPad. If you're somehow doing 4k video on an iPhone 6 I presume you're using some third party App. Not sure how it gets stored locally, and you'd want to ensure you can do this while at home successfully from that App.
But it's a built-in function. If you're willing to have your iPad as your storage, you don't need a thing.
https://support.apple.com/en-us/HT204144