Currently, I believe that they are only able to kind of make phone calls work which doesn’t even work so great yet and the camera not being able to work at all in anyway yet so this seems still a long ways away. From a person who isn’t optimistic practically ever in his life, I think video will have good audio and video sync, terrible camera quality, pretty low but not a horrific frame rate, poor audio quality and possibly bad echo for video calls.
If you are not satisfied with advice here on the forums or you would like a demo, try contacting the purism team via email and simply asking for a demo or if you think they may create a bias in their demo video, try contacting L5 owners to ask them to make a demo video when support for the camera to work is added in the next software update. If no L5 owner here wants to do something like that on here, search up those that have done testing with the L5 on youtube and ask them there or on their other social media.
edit: it is info@puri.sm for general questions and other emails are shown on this thread: How to properly send emails to Purism