M3 battery drops by 10% every 1 hour. Is this normal?

Consider using Activity Monitor to identify some possible energy-demanding culprits. Instructions: View information about Mac processes in Activity Monitor - Apple Support.

The Energy tab can reveal a "hall of shame", as does sorting processes by %CPU in descending order. Try both, and post a screenshot if you desire: View information about Mac processes in Activity Monitor - Apple Support. How to capture a window or menu describes a quick way to capture only the Activity Monitor window while excluding other information on your screen we don't need to see.

I also suggest you select Active Processes from Activity Monitor's View menu, because inactive processes are unlikely to be contributing factors.

Comparing your Mac battery usage to another person's battery usage is not a fair comparison. You have 90 days of free Apple phone support with that new M3 purchase, and you should talk to Apple support about your battery usage and how you are using your Mac, including the applications used.

I question the quantum of battery drain (3%) reported on an M2 MacBook for an hour of Netflix streaming via a browser. In my own experience, it is greater than the reported percentage.

Losing 10% per hour is not unusual for some activities such as having several browser tabs open with graphics or animation-intense websites. Some browsers other than Safari (e.g. Chrome) can be resource hogs and attack your battery more aggressively.

One thing that can greatly impact battery life is how bright the display is. If you have it blasting at a full 100% it will consume a whole lot more power than if you were to cut it back to 60-70%.

... And what should I do to maximize capacity so that I can use it for longer duration without having to charge it?

Read Batteries - Maximizing Performance - Apple

... my battery percentage drops by 10% every hour with just web browsing

With Safari?

Or...?