I'm not from Laminar Research, just a fellow simmer in the UK and definitely not a real world pilot!
My experiences so far with X-Plane 11 have been flying the Zibo mod 737-700U, 737-800X, 737-900U and the LES SAAB340A and so far, everything seems pretty realistic to me, including all of the relevant FMC's involved.
I have recently purchased the Flight Factor 767 Professional Extended Upgrade from XPlane.org @ https://store.x-plane.org/Boeing-767-Professional-Extended-Upgrade_p_896.html for $92.00. The Boeing 767 does not come as a default aircraft in X-Plane 11, so you have to purchase it separately.
As I'm still learning on this aircraft type in a simulator environment, I'm not sure of the different nuances between the various FMC types in the 767 i.e. Pegasus/PIP, but purely from a point of view of function and accuracy, I'm sure that your experiences will be extremely good ones, given that you will be using a non-professional simulator.
Here's a photo of the FMC's in the FF767 for you to take a view on?
You will see from this, that in the settings page, there is the option of using the 'original' version or the PIP version?