hi, i use reaper live onstage as a midi module rack, heres a long video of the setup:
https://www.youtube.com/watch?v=l5ar_3nGx2w
i had to really kludge the muting/soloing to get the most out of it and it doesn't even work on newer versions of reaper, for some reason the direct send doesnt work but routing thru another track and then to where you wanted to send does
what i was thinking was how cool it would be if there was a version of reaper designed just for this
ideally the thing you want is for for everything to be muted, and not using cpu, except for the things you're actually playing thru.
i couldn't figure out how to absolutely get that so i mute AND solo all the vsti tracks and then i have all the "preset" tracks muted and solo the one i am using.
thanks!