If I understand you correctly, you are just trying to record some stuff (MIDI?) and also keep the CPU load down with 0ms latency? One trick, while a bit time-consuming, is to bounce (render) the mix you have to a stereo track with the processing on it you want. Kind of a "ruff mix". Then disable all your tracks with native effects on them and just record your parts along with the stereo ruff mix. After you have recorded the parts you want, disable that stereo ruff mix or delete it - it was just a scratch track with low CPU to make your overdubs. Make sense?