Dragon Ball Z is both anime and manga. The anime was adapted from the manga and they share the same story and characters, but presented in different mediums.
The manga and anime have some similarities and differences. In general, they share the core storylines and characters, but there are small variations in details and pacing.
The common dimensions for a Dragon Ball Z manga volume are approximately 7 inches wide and 10 inches tall. However, there could be slight differences based on specific releases and printing regions.
Sorry to disappoint you. The Dragon Ball Z manga is not ongoing. It had its own definitive ending, but its popularity continues through various forms of media and merchandise.