I have the Dell 7567 using it for editing so I'm planning to get a 4K monitor. Is the HDMI port will output 4K/60fps? Is it HDMI 2.0? And I'm also planning so installing an NVMe SSD but most of them are PCIe x4. Is this laptop using on PCIe x4 or x2?
The product page here specifically says HDMI 2.0, so yes it will do 4K at 60 fps. I'm not sure about HDR, though. HDMI 2.0 certainly supports it, but I'm not sure if the GPU does. As for PCIe lanes, it's not just the number of lanes but also whether they're run in power saving or max performance mode. The XPS 13 9350 and 9360 for example both have an x4 connection but they run them in power saving mode, which gives essentially the same performance as a x2 connection. I'm not sure about the 7567's configuration, if you don't get an official response, see if you can find disk benchmark results from someone who tested a known fast SSD in that system. If the sequential reads max out around 1.8 GB/s, it's either x4 in power saving mode or x2. If you see 1.9 GB/s+, then it's x4 in max performance mode.