trying to understand what’s possible with ERC-721 tokens as NFTs

Hoping someone can help a beginner understand how the ERC-721 token works when a new NFT comes along promising future benefits, membership, etc. So, for example, let's say I launch 10k new NFTs as ERC-721 tokens on OpenSea.

Then, 6 months later, I want to send every holder another token, give them virtual membership to some game or site, whatever – how does this all work? What's possible and what isn't possible? Where do ERC-1155 come (or are those overkill for this?)?