I built a PC with following spec
Ryzen 3 3200g
MSI B450 Mortar Max
Corsair 1x8 GB 3000MHz RAM running at 2666MHz (No gameplay just for regular office use and web surfing and coding ).
Samsung 860 Evo 250 GB
Monitor Benq GW2283
I installed Pop OS 18.04 with latest kernel 5.x.x. All system hardware detected easily including integrated gpu. But the gpu performance is not up to the mark. There is lagging while watching videos. There is no any kind of smoothness. Even while scrolling there is lag. I checked it on other monitor also but the problem is still there.
I tried ubuntu mate and manjaro also. But same issue. When I tried live solus there is no such kind of issue. Video play smoothly. And kernel version of solus is 4.20.16.
What is the cause of this issue. One more thing 2GB of RAM is assigned to igpu automatically.