Nick, I don't know how other people run RME but I run everything flat. I would think most people don't use volume on RME going into a preamp, I could be wrong. I set mine to 0.0, anything above doesn't sound as natural in my system. Sometime I will back bass down to -0.5 and notice more detail maybe the bass is stepping on the information on some recordings but 98% of the time 0.0.
I also run balanced cables to preamp and also rca's to preamp out of the RME at the same time. Each cable has its own signature sound. My rca is a little warmer and rolled off so if I'm in the mood for a more rolled off sound I change inputs selection on the preamp for a different presentation.
Just learn to navigate the menu and use what sounds good to you, set up your EQ you can turn it off and on on the fly with the remote. I found that as little as RME is it still responds very well to footers and it's platform.