An ERC1155 token can have multiple tokens while ERC721 tokens will always be unique.
As to when you would like to run a snapshot that’s totally up to you but it sounds like you are looking to do so once the tokens have been distributed.
Thank you, I am planing to make a campaign for the collectors who own a number of tokens to get one rare token from the collection. And I need to use the Snapshot Tool to get the verification that the collector have already collect that number of tokens, that’s why I am asking if the collector collected 3 ERC721 tokens (1,2,3) will it show in the Snapshot Tool that this collector owns 1,2,3 from the collection.