I used to play games on laptops. Easy, convenient but let us think about it. Yes, nice specs on the new one, but for how long? You cannot upgrade so "what you have is ........ what you have" kind of thing and once outdated it becomes a very expensive paper weight or retires onto someone's office desk to run spreadsheets and browse the internet and if you are lucky it can still run the latest windows (Seeing MS cancel support daily now a days) and read a bit of email possibly on Gmail web view since outlook will be too advanced for it. Harsh reality.
Desktops on the other hand is upgradable. You can up on CPU, GPU, RAM and when that fails to keep up, you replace the mother board, and you are set again for a few years.
Can it run all games.... probably not. Laptops in general are prone to overheat while gaming. Currently I think Alienware has the best laptop temperatures during game play (I could be wrong here but recall something like that). So, if the game is working but you are running it at max settings, it will somewhere begin to throttle to protect the system.
From my side, give the laptop a miss and get a desktop if you are going full on gaming. Stil your choice but that is my advice.
Edit: BTW, why downgrade to Coffee lake? (Gen 9). Added if I remember correctly on Gen 9 CPU's the GPU was a renderer and shared your RAM same as your iGPU. Someone might be able to shed a bit more light on that, but looks more like a down grade as opposed to an upgrade. Only thing you are really gaining is 16Gb Ram, but the rest you are pretty much down grading. Gen 10 (Going on memory here) would have been an Intel UHD or 620, maybe even a 630 iGPU as opposed to Gen 9 was a UHD 610 or 615. Also, Gen 9 was split into two. You will need to check if it is gen9 first or second version. Both sockets are the same, but chips are not interchangeable. Think you might need to do a bit more research on this downgrade.