Yes, it is the possible to use the PlayCanvas to create online multiplayer games as shown by http://www.tanx.io, https://blastarena.io/ and https://robostorm.io/
As for whether it’s a good choice for a beginner, probably not due to the size of the community if you do get stuck. Unity with a SDK like PlayFabs or Photon may be a better choice due to large communities but the actual task itself is no more/less difficult.
Making multiplayer games is a difficult task due to the number of issues you can run into no matter the technology.
If you do want to continue on with PlayCanvas, I recommend reading this post: Real Time Multiplayer Tutorial