I had this problem before. Project settings didn’t work at all. Max FPS was locked at 60FPS, and delay always 18+ ms.
You will find not only Unreal Engine but also some games have this problem.
Solution: It’s cause by NVIDIA Experience settings. To solve this problem just need to uncheck NVIDIA Experience->settings->games->Battery Boost. After that go to Unreal Engine project settings->engine->general settings->framerate and check smooth frame rate. Now you can set max FPS at any rate and the time delay go back to normal at about 8ms.
Hardware:
laptop(MSI, Only one video card could be used at the same time)
CPU:i7-7700HQ
RAM:DDR4 2400MHz 8G*2
Harddrive:SSD+HDD
GPU:GTX 1060 6G
Software:
windows 10 16299.192
Unreal Engine Version: 4.18
EDIT:
Unfortunately, I found that I have to Uncheck and then Check “smooth frame rate” every time I reopen Unreal editor, or it will still focus on 60FPS and over 18ms. Hope someone could find a perfect solution.