Given a certain key, let's say it's a string, is there a way for clients to subscribe to any changes to that key without doing the pub sub pattern, or do I have to explicitly "publish" the key as a channel every time I change it for any subscriber to pick up the changes?
This question has very little context making it hard to try and work out what exactly you're referring to. Including class names, APIs, sample source code, etc will help identifying what you're asking. Please also label questions in the appropriate category.
You're taking about Redis PubSub? I don't know what key changes you're referring to, but Redis Pub/Sub is not related to keys stored in Redis, clients are instead subscribing and publishing to channels. Please read Redis Docs on Pub/Sub for background on what Redis Pub/Sub is and how it works.