it is 'easy' to find a place for Mt Cook or Lake Pukaki

but reasonable expensive for both. on the other hand, lake Tekapo had plenty of choices and less expensive. (dont know much about Twizel). Three are not far from each other. And yes, Lake Pukaki is beautiful (as many lakes in nz), but for a 'perfect' photo opportunity, you need luck: no wind and sunny, etc. if you see a 'perfect' opportunity, dont miss it because it wont last. I missed one (not easy to stop) and it never came back for me...