I have an Elecraft K3-Line setup with a K3, KPA500, KAT500 and P3. The K3 has an IF tap coming out the back from the 2nd stage filter. This is an 8.125MHZ signal that can be directly feed into the SDRPlay RSP2 Pro.
I use WIN4K3-Suite as a Rig control but also WIN4K3 provides a pan adapter and a series of virtual serial ports so that I can run multiple programs at once. My normal setup for software is the WIN4K3 Suite running with the pan adapter open. I have HRD Log open which directly interfaces with WIN4K3. I also have CWSkimmer open for broad spectrum CW decode (20 kHz and 400+ simultaneous QSO's). I am now also keeping WSJT-X and JT-Alert open as I am active in the ARRL Grid Chase. As of this minute I am tops in the state of Missouri but K1USA is very likely to overtake me! I would love to tour his station, it must be a beast.
I can also open N1MM for contesting, MMTTY for RTTY, FLDIGI and a host of other programs. I love using Scott's software for backup logging and contesting - N3FJP http://www.n3fjp.com. They offer a tremendous suite of contesting and logging programs.
Back to the RSP2-Pro: What an amazing device. I am able to see the entire band spectrum such as the entire 20 meter band at once! I can click on the spectrum and the radio will instantly move to the station I selected. Everything works seamless thanks to the WIN4K3 Software from VA2FSQ: https://va2fsq.com/
Well thats it, I hope this discussion was helpful. Please reach out if you need any assistance with the setup and settings.