I have an i7 and a GTX 1080 ti. I tested WOT Encore RT at several different resolutions and settings. My results with RT on at the highest setting compared to RT off are 40-65% lower FPS at most resolutions. That a huge performance hit for better tank shadows. I used MSI Afterburner to record average FPS, minimum FPS, 1% low FPS, and 0.1% low FPS.
I began testing it on a lower spec system. I'm not done, so I don't have all the results yet, but it looks similar.
Also, Wargaming is lying to its customers. It gives sub 30 FPS results a "Good" rating in their WOT Encore benchmark. Most players wouldn't consider a near slideshow of sub 30 FPS a "Good" gameplay experience.