Yes! You can add additional Arlo cameras to your existing Arlo account.
While local storage is an option, without a subscription plan, you will not receive any of the other great benefits of Arlo Smart, like package detection, activity zones, smart notifications and more. For more information on Arlo Smart, take a look here: https://kb.arlo.com/000056583/What-is-Arlo-Smart-and-how-can-I-benefit-from-it
I believe that it has a max of 5 cameras per base station.
You can place your Arlo camera a maximum of 300 feet (90 meters) from the SmartHub or base station. The maximum line-of-sight range of 300 feet is reduced by each wall, ceiling, or other major obstruction between the camera and base station.
Yes, you may download ARLO app for field view.
I have had mine installed for a week now and its gone down 5% battery life. I have the solar panel on another camera and its fully charged every day.