Device compatability

I use zoom for dance classes. I have three questions.
1. Many students are facing similar glitches in the video. My video is seen instead of theirs. It is broken by lines and the colours also change. What is the solution to this?
2. I would like to purchase a new laptop. My requirements are a good microphone that can catch sounds of instruments and singing, and also a wide-angle camera without distorted sides. Can you suggest a laptop that would be appropriate and compatible with zoom?
3. If I am instructing and the student is dancing, how can I make sure that the student is visible in the recordings?
Thank you