The decision one would make on topics really depends on the use case. If your entire system architecture has a clear delineation across customer/article or across created/updated/deleted, then it could make sense to split the topics along those same lines. If not, then there may be less use in splitting into multiple topics.
One way to determine how to do the split could be to consider the type of each message. If you split across all these topics, would they all have the same type of message (maybe an "event" message) or are the message types going to be different? If they are different, then different topics may make sense.
Most interesting might be the behavior on the subscribe side. Will the same subscriber be interested in events for both customers and articles or are their different subscribers for each? What about create/delete/update? A split along these lines sounds less likely. If all subscribers are going to be interested in all messages, then a single topic is probably reasonable. Otherwise, a subscriber will have to receive messages from multiple subscriptions. If some subscribers are interested in a subset of messages, then separate topics (and therefore, separate subscriptions) could be beneficial. Otherwise, the subscribers will have to look at all messages and immediately ack the messages they are not interested in, since Google Cloud Pub/Sub does not support filtering at this time. If it is a mix, then it is a tradeoff between more complexity in the subscriber interested in all messages (using different topics) and complexity in the subscriber interested in a subset (using the same topic and having to filter).
