What is the Difference between Google Analytics 4 vs Universal Analytics?

Universal Analytics hit types include page hits, event hits, ecommerce hits, and social interaction hits. In contrast, Google Analytics 4 data is event-based, with the principle that any interaction can be captured as an event.

the method of calculating the number of users, essentially taking into account active users, and the report templates ?!

Unisersal analytics is more comprehensive if you have an app plus a website. It is able to track the interactions between the two.

Don't know much about it, but this is a hot topic among website owners these days.