Hi, yes, there is a built-in 10-min break, during which you can use the bathroom. This 10-min doesn't count against the 240min exam time, which means you get 240min +10min break. No paper or pen is allowed.
Here is the link to the OnVue online whiteboard, you can practice with it beforehand.
home.pearsonvue.com/onvue/whiteboard?_ga...#practice-whiteboard
Here is the link to the OnVUE online proctored exam policies.
home.pearsonvue.com/pmi/onvue
Hope that helped. And there is tons of online exam experience shared in the Lessons Learned section. Those posts covered a lot of details. Good luck!