There is no physical base in Flared: it doesn’t simulate real light or lenses, even if it's able to add lens dirt. It is an artistic instrument to add drama and cinematic effects to your renders and animations.
No, Flared comes now with 9 templates that you can highly modify using the sliders of the editing panel. You can save your presets and recall them in other projects. Here is a video about the use of presets.
Yes, you can try, but at your own risk, because we can give you assistance only if you use the official stable version of Blender.
Now it works only in Eevee. This is due to the material node "Shader to RGB" that is not compatible with Cycles. Anyway, there’s a trick that can be helpful to have it in Cycles too. You can find here a video tutorial about that topic.
You can install the .zip file in Blender from Preference/Add-ons/Install... Select the .zip file, install and activate it. It will appear on the right sidebar in the viewport (if you don't have it, press the N key), as a tab named Flared.
We have tested Flared on Mac, Win and Linux. If you can work in Blender 2.81 and higher on your system, you'll have no problem using Flared.
Sometimes you can have glitches due to too high emission settings, or too high or too low dimensions settings, but it’s very simple to solve it playing with the sliders. In the past, we've had problems with volumetrics, but they are solved now. Still there be an issue due to the use of DOF. In this case, there are some actions that can solve the problem. Here is a video that shows the advanced editing techniques that you can use to solve some rendering issues or to achieve different effects.
There is a deprecated version of Flared that was good in 2.80. But it's discontinued. Flared now works only with Blender 2.81 and higher versions. If you really need it in Blender 2.80, please, contact us.