Rendering Aspect Ratio
Fusion 360 defaults to the viewport aspect ratio when rendering images. This often creates images that are extra wide and not very usable. It is better to select a specific aspect ratio for your rendered images. You can make custom ratios but to start off stick with the following aspect ratios 1:1, 3:4, 16:9 all in either vertical or horizontal orientation. Aspect Ratio Demo Video
Cloud Rendering vs Local Rendering
Rendering in the cloud costs credits but can be faster than a local computer, especially for multiple renders although there is an initial wait for the cloud render queue.
HDRI Environment Photos for Render Backgrounds
Here is a generous website of Greg Zaal, a CG artist offering their HDRI photos for free. They are licensed under CCO. The artist asks for credit to be mentioned so please do that but you can use these photos for any use.
Download the photo that you want and then you can attach a custom environment in the Fusion 360 Render environment. Then you can use it as the background for renders of your models. This video shows how to insert a custom HDRI background.