I am making my first project. In MacOs when you open the AudioPluginHost it shows two options->
Scan for new or updated audiounit plugins
Scan for new or updated VST3 plugins
but for windows its shows (2) option only.
I have already built the 3 project files → Sharedcode, StandalonePlugin, VST3.
and manually put the vst 3 files in the common files.
I’m not sure if you are mixing up AudioUnits and audio plugins in general here?
There are a number of common formats for audio plugins in general, the most important ones are:
VST(2): The format that started it all, created by Steinberg, available for all operating systems. Steinberg wants it to disappear, so you are not allowed to build new VST2 plugins unless you signed a contract that allows you to do so a few years ago. Sometimes people use VST as a synonym for audio plugins in general
VST3: The successor of VST, also created by Steinberg. Available for all operating systems. Probably the most future proof format, supported by nearly all mainstream hosts today
AudioUnit (AU, AUv3): A format created by Apple and therefore only available on macOS. Most DAWs on macOS can load them, Apples DAWs like Logic, GarageBand and MainStage don’t take anything else than AU.
AAX: A format created by Avid, available for macOS and Windows. Only Avid hosts can load them, and Pro Tools, one of the most popular DAWs in the professional sector won’t take anything else than AAX.
A JUCE plugin project can be used to create all formats from within the same project and sources – which is one of the main selling points of JUCE. So you basically can just develop your plugin in a format and operating system of your choice and then easily build it for other formats and operating systems later from the same code.
Also keep in mind that e.g. a VST3 or AAX plugin built on Windows won’t run on macOS, so in case you want to support macOS at all you need a macOS build machine anyway
Just FTR: there are also linux plugin formats:
LADSPA
LMMS
LV2
VST3 (if compiled for/on linux)
I don’t use any of those, so somebody else would need to fill the details.
I don’t know about the current state of affairs regarding juce plugins on linux, there was some movement lately but I didn’t follow.