Using these tools you can observe the number of views per subscriber, as well as the growth rate of any channel. Look for how many views a channel has compared to the number of subscribers they gain over time. This will give you a sign of the quality (and engagement) of their content.
Some channels upload a lot of videos. But, it's worth assessing how much value each video brings to their viewers and their business. Do their videos get people to take action and become subscribers or customers?