Yes, you will see a performance impact and will need to make sacrifices. I don't recall what my exact settings are in x-plane. Here's my system setup:
i7 9700k @ 4.9 GHz, 32 Gigs of ram at 3200 MHz, 2x GTX 1080, 1000w PSU, and x-plane is run on a seperate 1 TB SSD away from the windows SSD.
I run 3 Scepter 27“ curved LED monitors along with a SIIG DP 3 HDMI port display hub. Even though I have plenty of ports on both cards to run all 5 screens on their own, I found it impossible. I need to do some more research into this but just haven't had the time. For some reason when I ran all 5 screens independently on their own port, Windows 10 would only recognize 4 of them, the 5th would remain blank. Once I swithced to using the 3 primary displays on the hub, everything worked fine and windows recognized all 5.
When flying in clear weather, I get on average 32 FPS in the TBM. As soon as clouds/shadows are introduced, I take a performance hit. This is of course expected and I decided to accept low FPS for great visuals during storms. When major clouds are present, I can get as low as 16 FPS.
One thing I had to do to help improve my overall performance was to completely get rid of my OrthoXP library and go back to default XP textures/mesh. Once I did that I gained about 5 - 10 FPS. This actually worked out for the better because Ortho was causing elevation issues at many of the small fields I was flying to.
Eventually the plan is to upgrade the graphics cards to at least 2x RTX 2080, but that is a big expense. My next addition will be a DOF Reality motion platform but I'm still doing research on that before purchasing.