I have not tried version 16 so much (even the beta version).
From what I know, there was a major change in the way guest graphics were handled. They call it MKS Sandbox.
Version 16 provides DX11 (to Windows VMs) and OpenGL 4.1 to the VMs.
Version 15.5 provides DX10.1 and OpenGL 3.3 core profile.
Running with 15.x profile on version 16 software, you lose those capabilities (DX11/OpenGL 4.1 in guest VMs). I don't know what else you forgo.
One thing that is still the same from the vmware.log file is version 16 still uses the underlying graphics hardware to deliver the rendering engine. That's why it is better keep the default graphics engine to the Nvidia 1660 Ti Max Q as it is should be much faster than the Intel Iris Plus G7 graphics; albeit at the expense of battery power duration.
From mksSandbox-2.log
2020-09-16T03:51:03.856+08:00| mks| I005: MKS-RenderMain: Starting DX11Renderer
2020-09-16T03:51:03.891+08:00| mks| W003: DX11Renderer: Enumerating adapter 0
2020-09-16T03:51:03.891+08:00| mks| I005: DX11Renderer: `Intel(R) Iris(R) Plus Graphics` vendor=0x8086 device=0x8a52 revision=7
2020-09-16T03:51:03.891+08:00| mks| I005: DX11Renderer: video=128MB system=0MB shared=16179MB
2020-09-16T03:51:03.891+08:00| mks| I005: DX11Renderer: LOCAL budget 15411M usage 0M avail 7833M res 0M
2020-09-16T03:51:03.891+08:00| mks| I005: DX11Renderer: NON-LOCAL budget 0M usage 0M avail 0M res 0M
2020-09-16T03:51:03.986+08:00| mks| W003: DX11Renderer: Using device unknown; adapter `Intel(R) Iris(R) Plus Graphics`
2020-09-16T03:51:03.986+08:00| mks| W003: DX11Renderer: Enumerating adapter 1
2020-09-16T03:51:03.986+08:00| mks| I005: DX11Renderer: `NVIDIA GeForce GTX 1660 Ti with Max-Q Design` vendor=0x10de device=0x2191 revision=161
2020-09-16T03:51:03.986+08:00| mks| I005: DX11Renderer: video=5993MB system=0MB shared=16179MB
2020-09-16T03:51:05.212+08:00| mks| I005: DX11Renderer: LOCAL budget 5225M usage 0M avail 2740M res 0M
2020-09-16T03:51:05.212+08:00| mks| I005: DX11Renderer: NON-LOCAL budget 15411M usage 0M avail 7833M res 0M
I think if you set the default to Nvidia, adapter 0 should be the GTX 1660 Ti instead of the less powerful Intel Iris Plus G7.
Alternatively add the following to the vmx file to force the use of Nvidia for this particular VM.
mks.dx11.vendorID = "0x10de"