These tools do much the same thing. You use a web browser, or downloaded app to send live video from a web camera, and whatever is on your computer screen to students. The students can use a text chat window to reply. There can also be quizzes. All of this can be recorded for later replay. Students can also talk, be seen, and perhaps send what is on their screen, but that gets complicated), especially for large classes. You will want to at least have a moderator to look after the chat, while someone else does the talking.
I suggest using these synchronous tools sparingly, as a supplement to asynchronous online learning. That is, students should be able to watch a recorded video, read some notes, do some sort of exercise step, by step, in their own time. There can then be some synchronous (real-time) activities to help them.
What also helps are activities to connect students to each other online and carefully worded announcements from staff, to the class, to give the sense someone is out there. This is all part of the conventional approach developed for distance education over the last few decades.
The "Learning to Reflect" module I designed is an example of this approach. The students read the notes, watch the videos, do the quizzes, post to forums, and reply to other students, before the live part. The student gets all the notes at the start of the course. There are also suggested regular posts for the tutor.