Yeah I don't think we plan on getting the iPad on wheels any time soon but I do want to put some effort into the little things that can make audio/video/connectivity better. We use Slack and are happy with the calling features. Slack also acquired Screenhero so I'm excited for some of those features to get more integrated.
The "robot-iPad-on-wheels" was actually a lifesaver for our company - we didn't have the discipline to avoid the water cooler conversations or instantaneous whiteboard sessions, so having the robot be able to 'overhear' the conversation was actually immensely helpful for the remote person.
We just switch from Slack to Discord. The voice channels add an "office environment" feeling to just speak when you have a question. And it also has all the chat features of Slack/HipChat. The only downside is no integrations so if you need that then Slack is your best bet.