Theoretical question about 2 displays vs. 1

So I'm running X-plane really nicely on 2 27-nch monitors, both at 2560x1440.

Even with heavy payware (Flightfactor 757, for ex) I'm maintaining between 25-30 frames, with sliders mostly to the right. (reflection detail is only one off.) Also HD terrain mesh in much of the U.S.

But there's now an LG 49-inch monitor with 5120x1440 res.

It costs quite a bit, but I'm wondering whether running ONE display at that resolution would be easier for my machine (and thus give me more frames) than my current setup, with two running at 2560x1440.

Any ideas? An experiment with switching one of the monitors to "unused" in X-plane and switching the other to 5120x1440 resolution does not really improve performance... but even under that scenario, the vidcard is producing an image across two monitors, right?

Not sure about that one.

But any advice would be appreciated. Thanks!

My machine is a Dell Alienware Aurora R8, with an i7 9700 and a Geforce RTX 2080.