Battery life in Macbook Air M1.

So it means that the problem among all my applications is google chrome?

It is only one contributing factor, but it is probably the most common, which leads to your next question:

Should I start using Safari more?

It's up to you, but bear in mind Google Chrome is only one part of an overall Google infestation. You cannot use Chrome without installing all of Google's invasive system modifications. If you need an alternative to Safari consider using Brave, which is a Chromium-based browser that does not carry the burden of Google's continuously running, information-harvesting and automatically updating processes.

https://brave.com/

There are other Chromium-based browsers. Microsoft Edge and Opera are probably the most common, but I have no meaningful experience with either one.

And please can you determine how many hours of battery life can I get based on my mentioned usage.

It cannot reasonably be estimated, because everyone does different things with their Macs. Apple publishes expected battery life specifications based upon very specific criteria that no one is likely to duplicate all the time.

I seem to get anywhere from 4-10 hours at the most, I literally only use Mail & Brave. I didn't do much research beforehand and assumed this model would beat my 2015 MacBook Pro for battery life... a little disappointing!

Google has always been a notorious resource hog. You can expect its many automatically updating processes and "helpers" will result in approximately 50% reduction in battery life from what might normally be expected.

Installing Google on a Mac obviates most of the reasons for having one. If you are required to use Google buy a Chromebook.