Question turn on the Bloom, the thin Emission looks strange.

Unity 2021.3.0f1 version is in use.
Changing Bloom's quality to low makes the problem worse.
The first image is of high quality and third image is of low quality
I think it's a camera setting or Bloom problem, how should I solve it?

 

The issue you're seeing is caused by the bloom not having enough information to properly calculate the effect. The two biggest things that will contribute to undersampling like this are low rendering resolutions and thin objects, like planes. Both of these are directly related as you can get away with thinner objects the higher the resolution is.

You should be able to get similar visual results without the artifacts by making your object a little bit thicker and lower the intensity or scattering of the bloom to compensate

 

In addition, energy conservation does break physically based if the threshold is set to anything but 0, so it'd be a good idea to know exactly what you're trying to achieve here in the scene betweens artists tweak and physically based standards


Regarding the quality presets themselves, they are values that are set in your global pipeline asset.

If you have to use low, for hardware limited reasons you can check the pipeline asset to see exactly what the low preset is with samples etc to give you and idea of where you're at the moment, you may have some wiggle room.

However just be aware that it really takes Some thought and understanding of hardware and debugging to change these particulars.
Unity tend to give so safe conservative values in general.