It is perfectly acceptable to communicate outside of Upwork and it's quite common.
Just ensure you are logging your hours properly using the Upwork tracker. Meaningful memos and levels of activity when you are "on the clock." That's where your most important protection is.
Yes, the Upwork video function is very ineffective.
The key thing is to not begin any work until you have an accepted contract (client sends offer, you accept) to begin work.
Since you are new here, I would recommend that you read up on these these tips for avoiding questionable jobs, paying close attention to the Safety First! section of the resources, for more information about working safely through Upwork.
You may also want to read up on this help article for more information on what actions may cause yoru account to be temporarily or permanently suspended. I hope this helps!