Macbook 16 inch 2019 Pro 2.3 GHz 8-Core Intel Core i9 - overheats with external monitor

Are you using the computer in CLAMSHELL mode with an external monitor?

If so, and you have the computer vertically to get it out of the way, you must have the hinge side UP. The hinge area is where hot air is exhausted. If the hinge is down the hot air is trapped inside the case and you get symptoms like you describe.

Cool air intakes are on the sides so they must not be blocked either. You can't shove one edge of the computer again the back of the bookcase and expect the computer to stay cool.

Interesting that Apple appears to have removed support references to using a notebook computer in clamshell mode from the support library.

This article may help: Keep your Mac laptop within acceptable operating temperatures - Apple Support

Post an etrecheck report so that we can see what may be contributing to slowness and "text lag".

Using EtreCheck - Apple Community

MacBook Pro 15 2015 i7 16GB often got hot and made noise, tried cleaning it, updating thermal paste, resetting the SMC, reinstalling the OS, disabling animation, switching to the old Catalina OS, cleaning startup... there was 0 effect.

Here's what helped:

1. Install the free application "Turbo Boost Switcher" and click on the "Disable Turbo Boost" function.
2. Install the free application "Macs Fan Control" and configure both fans in it - "Sensor-based" in a temperature mode of 60°C and 85°C. The first fan was installed on the CPU Proximity, the second on the Intel Iris Pro GPU (or whichever one you have).

After this, the fan noise disappeared. The temperature is not rising. Productivity has not decreased. I ran high-load tests with these parameters and they all passed successfully.

It feels like I bought a new Mac.

MSDOSya wrote:

1. MacBook Pro 15 2015 i7 16GB often got hot and made noise, tried cleaning it, updating thermal paste, resetting the SMC, reinstalling the OS, disabling animation, switching to the old Catalina OS, cleaning startup... there was 0 effect.

Here's what helped:

Install the free application "Turbo Boost Switcher" and click on the "Disable Turbo Boost" function.

2. Install the free application "Macs Fan Control" and configure both fans in it - "Sensor-based" in a temperature mode of 60°C and 85°C. The first fan was installed on the CPU Proximity, the second on the Intel Iris Pro GPU (or whichever one you have).

After this, the fan noise disappeared. The temperature is not rising. Productivity has not decreased. I ran high-load tests with these parameters and they all passed successfully.

It feels like I bought a new Mac.

Third party apps are not needed to manage or control a Mac. The MacOS handles these tasks very well.