You probably will need to use POST or PATCH, because it is unlikely that a single request that updates and creates multiple resources will be idempotent.
Doing PATCH /docs is definitely a valid option. You might find using the standard patch formats tricky for your particular scenario. Not sure about this.
You could use 200. You could also use 207 - Multi Status
This can be done in a RESTful way. The key, in my opinion, is to have some resource that is designed to accept a set of documents to update/create.
If you use the PATCH method I would think your operation should be atomic. i.e. I wouldn't use the 207 status code and then report successes and failures in the response body. If you use the POST operation then the 207 approach is viable. You will have to design your own response body for communicating which operations succeeded and which failed. I'm not aware of a standardized one.
