Here are first notes about this: the amount of videos shared in teams won't change the quality in general, at least it should not.

Here is how to break down possible issues: 
  • If connection quality is bad in all videos, it is in most cases your computer or network conenctivity. 
  • If there are only some it's mostly related to their individual connection quality. 
  • If you have problems in any way, it is only your quality it is yours. 

Also kinda something that we forget, your quality and internet speed won't affect others video and quality.

Always nice is to install a bandwith meter or something to monitor the traffic flow on your computer. Speedtests are great, but as thy swallow a lot of traffic it might not be ideal when on a mobile phone plan or with limited traffic. 

Monitor the traffic flow does not mean monitor the content of the traffic but the speed that is happening in the background.