It is absolutely possible to run triple monitor setup alongside VR.
I used to have triple 1080p displays with Samsung Odyssey+ headset (HDMI). That setup also worked with HP Reverb G2 (DP) when I tried it. I currently have 2x1440p and a single 4K all connected via DP and the same old Ody+ via HDMI and it all works. If I needed to connect a headset with DP input I'd just have to switch one of the monitors to HDMI, I haven't tried that, but I'm positive that it will just work.
If you have any issues I'd suggest to use DDU and then reinstall the GPU drivers from scratch.