One of the coolest things about REAPER is its routing capabilities.
So, for example, to set up reference tracks in REAPER, an easy way to do it is to load each of your references on their own tracks, and mute them.
In the routing window, uncheck the send to the master/parent track. Instead, put a check in the routing matrix to send it directly to the same output as the master, but bypassing the master altogether.
To audition any of your references, just solo them. Clicking solo on and off allows you to quickly hear how your mix compares to the reference.
Doing it this way bypasses all the fx you have on the master buss. Adjust the volume on your reference to volume match your mix.