1) A dedicated GPU in a laptop, specially a thin one like the X1 Carbon, is a bit of a nightmare. It consums a lot energy, it needs a lot of heat dissipation, and it can even reduce the life span and robustness of the laptop.
2) The X1 carbon is not targeted at video games/video editing. It's targeted at usages like programming or word/excel editing. For these use cases, integrated GPUs are more than good enough.
3) Dedicated GPUs tends also to be a little bit of a nightmare, specially around managing drivers. This is particularly true under Linux. On one hand you have Intel GPUs with open sourced drivers directly in the main line kernel. On the other you have the Nvidia drivers, which are proprietary, requires DKMS and can stop supporting older models, and the ATI version is about the same.
4) if you really need a dedicated GPU, the W serie is for you (and maybe some T serie laptop as well).
Given that the X1C'18 has a proper 4 PCIE Lane Thunderbolt, just buy an e-GPU if you need decent gaming - e.g. go to a LAN party, that kind of thing.
Considering it has a proper quad core CPU in such a thin frame, it's the best of both worlds really. The external GPUs really sort out the thermal issues when gaming on a laptop.
I have the OG X1 Carbon, still going well - glad I got the i7/8/256ssd model which was top of the line when it first was released (i7 was actually only avail with 4gb so bought i5, but then I had to return it due to a chassis issue; by the time that was sorted, the i7/8 was available!).
I run Win10 on it now which is perfect; had to disable the trackpad when I used Linux a few years ago. Love the Trackpoint, can't see myself upgrading to something that doesn't.
2) The X1 carbon is not targeted at video games/video editing. It's targeted at usages like programming or word/excel editing. For these use cases, integrated GPUs are more than good enough.
3) Dedicated GPUs tends also to be a little bit of a nightmare, specially around managing drivers. This is particularly true under Linux. On one hand you have Intel GPUs with open sourced drivers directly in the main line kernel. On the other you have the Nvidia drivers, which are proprietary, requires DKMS and can stop supporting older models, and the ATI version is about the same.
4) if you really need a dedicated GPU, the W serie is for you (and maybe some T serie laptop as well).