x16/m16, question about multi-monitor support?

The ports should have the same hardware support, but note that Alienware systems aren't designed to be dock-compatible.  You would likely be better off with a Precision workstation, which does have dock support.

@ejn63​ do you anything about multi-monitor support? It is really capped to two monitors?

Not by hardware, no -- but Dell doesn't support any docking stations with Alienware models, so you'd be on your own if you have trouble with one.

That is why I suggest you purchase a model that does have Dell support for a dock, if you plan is to use multiple monitors.  There are Dell systems that do support Dell docking stations.

X16:
1 USB-C Thunderbolt 4.0
1 USB-C 3.2 Gen2
1 HDMI 2.1
1 mini DP 1.4

m16:
2 USB-C Thunderbolt 4.0
1 HDMI 2.1
1 mini DP 1.4

You don't need a dock to connect 4 monitors.
In both models you can directly connect each monitor to each of the ports using only cables, no need for adapters.
Attention that probably the Thunderbolt ports should be connected directly to the iGPU in both models.
All other ports, including the X16's USB-C 3.2 Gen2, must be connected to the Nvidia dGPU.

Edit:
I just now noticed that Dell states that both laptops only support 2 external monitors. 
I'm sorry... 

From my personal experience with Dell laptops this may or may not be true...just testing to be sure. 
About Dock TB, I believe it can work for monitors. 
For the m16 it certainly won't deliver power since its USB-C ports don't have that functionality, but for the X16 it may deliver 130W. 
I've seen reports of this dock working on X15 R2...

@pedrohenriquevm​ it is very confusing, nothing is limiting this laptop to support 4 monitors hardware vise. But Dell only listed support for 2 monitors support.

Maybe someone from Dell can answer?

‎FAQ Alienware Laptops | DELL Technologies. 

Which ports output dGPU (discrete graphics processing unit) ?

NO means the port is using the iGPU Intel. 

.

@crimsom​ thank you! So TB port is not connected to dGPU on x15 r2/m15. I understand it means that dock station will not work for me (4x4k@60hz). I can try to daisy chain, but I think I will search for another model to buy.

Could you suggest Dell model that work work with dock that I mention and can support 4x4k@60hz monitors?

Hi user_b24fae thank you for sharing update. 

Advocate that you contact Dell Support for the official information so that you are not dissapointed. 

If system delivered with fault or incorrect specification, you have Reject option. 

‎Dell Refund policy, New vs Refurbished | DELL Technologies.