Currently the M1 Limiter is the only official FMOD McDSP plugin.
You can load VSTs (not VSTi) into game code by using System::loadPlugin and then System::createDSPByPlugin. You will need the 32 bit and 64 bit versions if you are building different versions of your game.
Please note that there are a lot of limitations when using VSTs. Firstly, only
.dll files can be loaded, not
.vst3. Second, you may not be able to get the VSTs running on different systems. Third, there is likely going to be a performance hit outside of FMOD’s control when using third party VSTs.
If you wish to be able to use a VST within FMOD Studio application it will need to be built it in a specific way to work with FMOD Studio and to expose its properties.