The plugin is currently supported on macOS, Windows and Linux as VST2, VST3 and AudioUnit (on macOS only). Note: AAX is likely never coming, as AVID does not seem to support open source projects unfortunately. See the compatibility section for a workaround.
With the AudioGridder FX plugin you can plug a remote insert effect chain into your DAW’s channel inserts. From there you can insert any FX plugin available on the connected server.
Instruments work similarly. Create a software instrument track in your DAW and select the AudioGridder plugin as instrument. Now you can load any of the instrument plugins available on the server.
Each AudioGridder plugin instance will connect to a single remote server instance. But each separate loaded plugin instance can connect to a different server, so you can connect to multiple servers from your DAW at the same time.