Tracking the changes to the Signal Desktop Application on the WhisperSystems github, it looks like they're moving to an Electron app (like Slack). Thumbs down from me for code bloat, but it'll be nice to have a separate app and not be required to keep Chrome open all the time.

Video calling on Signal works a little differently than WhatsApp to my understanding; it's decentralized and so the quality is lower, but the Signal server manages to keep from collecting any data, and backdoors can't be added (it just sets up the call and then bows out).