just posted this in a similar thread:
I received my MBP 16", i9, 32GB, 5500 8GB yesterday and did some testing.
I am an editor (FCPX) and the machine is indeed really fast. Everything works as expected, even quiet within FCPX for normal playback, the speakers and keyboard are nice. Everything's great... until... I plug in an external screen. Then the fans kick in all the time to cool down the GPU which heats up because it has to deal with the external monitor (in my case the 23,7 "Apple" LG 4K via TB3).
Very annoying. I was hoping to get a replacement for my MacMini 2018 (with Blackmagic eGPU) which is very silent, but the MBP is too loud for me. I really wanted to like this machine. And no, no Photo optimisation or other system tasks were going on like indexing because I did not import anything. 0-1% CPU on idle.
To test I tried hooking up the external display via the Blackmagic eGPU connected then to the MBP and as expected, the MBP is silent again because it is now the eGPU which is dealing with monitor now.
It is a great computer when you are on the go or don't need external screens directly connected, and here I mean real work like image or audio editing applications, no webbrowing or email, there the computer was more quiet even with external display.
All together this computer is not for me, I will stick to my mini+eGPU.
Will send it back.