You asked
Is the sony a9 ii good in low light?
The a9 II is a full frame camera, and that's its main advantage in low light. At the same framing and f-number, a bigger sensor gathers more light than APS-C, roughly a stop more. The site doesn't have high-ISO test results for this body, so I can't tell you how clean it looks at a specific ISO.
Your lens matters as much as the body in dim rooms. These fast options from the a9 II's list are worth a look:
If low light is what you shoot most, the Sony a7S III is built for it. Its 12.1-megapixel sensor is small for stills, though, so it suits video better.
Written by Claude from this site's pages.