Hi Ogs,
Convolution in HQP does take place in the main program. The NAA is little more than an Ethernet/Wi-Fi in and USB out buffer.
You can run HQP anywhere on your network and send it input from Roon. Roon asks for an IP address for HQP and defaults to “localhost” being the same machine for Roon and HQP.
As at November last Danny indicated there were no current plans to add VST plugins.