macbook pro 16" loud fan noises

Hello,

I recently got a macbook 16" i9 base model and realized there is fan noises issues when connecting to my external LG display. The machine works great and fan noise is low when is by itself. But when I connect it to the external monitor, the fan ramps up quickly even though I am doing the same tasks (browsing web, watch videos, write code, etc.) in both situations.

I tested the performance in both situations with iStat Menu and realized the big difference is graphics. In standalone mode, the built-in Intel UHD Graphics 630 is used; while connecting to external display, the AMD Radeon Pro 5500M is utilized and it instantly generate huge amount of heat for the same tasks and require the fan run at a high speed to cool it down. The fan noise is unreasonable and annoying for such as powerful machine.

What is causing the bad graphic card performance? Is there any solution to fix it? Thanks.