System: Zorin OS 18.1 Core (Wayland)
What are currently the best drivers for the NVIDIA GeForce 940MX?
Right now I’m using driver version 535.288.01, but I’m not sure if it’s worth switching to a newer version like 580 or maybe something else.
What are your experiences, and which driver would you recommend for this GPU, especially when using Wayland?
well in my experence I find that if what you are using works...then leave it alone...the new hotness isnt always the best to have...... 
Driver 535 seems right for this card according to the AI respons I got.
ya i would stick with it...in past i installed the so called"better" driver and had nothing but troubles and a heck of a time reseting it. of course now i use timeshift before i do stuff so i can revert back
I looked at the Nvidia website for the Card and it showed that the 580 Driver is compatible. So, it should work.
The Point is:
I personally wouldn't recommend using Wayland in Combination with Nvidia on Zorin. With an up-to-date Desktop Environment I would say that You could try the 580 Driver.
But when You now have the Combination of 535 and Wayland and it works fine and there are no Issues or Functions for what You need the newer Driver, I would say simply stay on the Driver.
You could try the newer Driver, too. and when You don't like it go back to the older one. That would be a Possibility, too.
On Zorin OS with NVIDIA, Wayland works better for me in most cases. I don’t have scaling issues like I did on Xorg.
On Xorg I also had serious performance problems. YouTube videos stuttered in every browser I tested, even at 720p. On Wayland, everything runs smoothly, even at 1080p.
I’m not sure about gaming performance since I don’t really play games on Linux.
Overall, the system feels much “smoother” on Wayland than on Xorg. What could be causing this? I have no idea. maybe fractional scaling, which Xorg doesn’t handle very well?
As I said: When that runs for You, that is what matters. Simply use it.
Do You have Fractional Scaling active?
Yes, I have fractional scaling enabled and set to 150%, because at 100% I can't see anything and 200% is too big.
Hmm i have glasses that do that too.....lol
Glasses are one thing, but at 100% scaling I literally can’t see anything on any screen. neither on my laptop nor on an external monitor XD
I honestly don’t know how people use Xorg when fractional scaling is such a pain there 
This is why many of us prefer XFCE. On Xorg, the XFWM Compositing applies DPI scaling, instead, just as Wayland does.
On Gnome, using Xorg, Fractional Scaling does not use DPI display, it renders the window at the original resolution, then scales that up the same way Zooming in on GIMP would look.
I actually have an Asus laptop with that exact GPU. I use 580 and Wayland on that one in particular after 550 expired. Blender works, though the initial login is slow, the rest is fine.
535 will lose support after June 
Is it possible to install the XFCE desktop environment with a Zorin OS–like appearance alongside GNOME, so I can test it without breaking my system and easily remove it if needed?
Yes, you can install the Zorin OS XFCE desktop, that includes the Zorin Themes and Zorin Menu.
sudo apt install zorin-os-lite-desktop
You can remove with
sudo apt remove --purge zorin-os-lite-desktop
After install, be sure to log out, then log in on the Zorin Lite Session.
In Zorin Lite, from Settings > Appearance > Fonts > Custom DPI setting
(The one in Settings > Appearance > Settings is integer scaling only)