The Mass Effect Trilogy is not graphically demanding. The Intel UHD 620 integrated graphics core would be enough to play those games at 1080p and default settings with decent results; 25 FPS to 45 FPS on average ranging between combat and simply walking around the Citadel. Lowering the resolution would provide better performance. The Witcher 3 is on a totally different level; it is a pretty demanding game.
I have never played the Witcher 3, but I would say that if you want good performance of 50+ FPS on average @ 1080p with medium graphics settings then a laptop with a GTX 1050 should be good enough. The GTX 1050 gets on average about 38 FPS on high settings based on several laptops tested by Notebookcheck.net. Click the link below for GTX 1050 info and game benchmarks. Each benchmark number you see is for a specific laptop.
https/www.notebookcheck.net/NVIDIA-GeForce-GTX-1050-Notebook.178614.0.html
Then nVidia mx150 is a "mainstream" dedicated GPU which is a step down from the GTX 1050, but will be in less expensive laptops. However, it is a big step down in performance in the Witcher 3. At 1366x768 resolution and medium settings the average FPS is 34FPS; depending on the specific laptop tested with the mx150, average performance ranges between 24 FPS to 43 FPS.
https
/www.notebookcheck.net/NVIDIA-GeForce-MX150-Benchmark-and-Specs-of-the-GT-1030-for-Laptops.223530.0.html