The sense of presence will be enhanced when everyone shows their face via their webcam. Consider requiring students to turn on video as a key part of participation, since it is easier to engage with the class if you can see them, and students are more likely to pay attention if they know they are on camera. The gallery view can be helpful here.

Consider permitting students to “stretch” every 20-30 minutes for 30 seconds. It can be harder to focus attention on a screen than in a classroom!
Polling features help see the distribution of perspectives on a particular question. When used well, this can be a powerful complement to the lecture or discussion. Apps like Poll Everywhere work great!
Webex’s Chat feature can be either very useful for the instructor, or a distraction if it is used continuously, so thinking about how and when to engage students is helpful.