First of all thanks for the details.
I wanted to test loopBeAudio and compare it with the RME internal loopback. When starting loopBeAudio it acts like a virtual audio interface and it has to be agglomerated to the RME one which was only possible using the ASIO4ALL driver which replaces the RME driver and induces additional latency. If you want to record vst outputs in GP you need to loopback the outputs you want to record. For now I use the internal RME loopback, but perhaps there is something interesting to do with this ASIO link.
Thanks again.