Logic is set to process buffer large with max buffer size of 1024 samples. Nuendo/Cubase is set to high priority/maximum boost for audio with max buffer size 2048. Reaper is set to give audio threads the maxium priority and request data with a block size of 1024.
Reaper is clearly the most efficient DAW mix engine to playback this mix (utilizing all 3rd party plugins). While the reported CPU usage looks far too low for Reaper, it nonetheless runs the smallest number of threads. The first available cores appear to be utilized more compared to how Logic runs the mix and the last few cores appear to be loaded less.
I don’t know of a workaround for the poor ASIO driver performance in Nuendo/Cubase that will enable the project to playback. CPU, memory and disk I/O resources on the machine are clearly not an issue.