Is there a way I can get the number of API's been hit and the amount of data downloaded by the browser when a page is loading?
I like to get the amount of data downloaded and the count using i.e Python
Maybe Selenium can help you with this. There is a post in which the use Selenium to get the network requests: Using Selenium how to get network request
Yes. You can export HAR file from your favorite browser and analyse it via python. HAR is just a JSON file so you can implement a script that will look for the data you are interested in.