Anything with graphics extensive usage (Blender, any simplest game/app with 3D) lags on external display (clamshell)

Recently I bought Philips 272E1GAEZ display. Important Edit: if I first power up macbook without external display, then close the lid and connect power and display - no lags whatsoever on the external display. The problem only when I first connect external display, then power up macbook, then open the lid to enter password (bluetooth keyboard not working on authentication screen), close the lid and use display with clamshell mode - lags happen. I read reviews about 144hz and wanted to try it out with my Macbook Pro 2019, 16". I connected it via HDMI. I tried Display Port -> Type C adapter at first, which gave me 165hz and Adaptive Sync, but after 1 hour of usage screen started flickering, switching off for 1 second (basically display port became unusable, no matter the refresh rate, after restarting macos 1 time I ended up with 100% CPU usage with fseventsd and unusable ANYTHING, lags were everywhere, imagine 3FPS, I don't know what was that but after restart they disappeared). So now I use 120hz and 1080p resolution via HDMI port. (changing refresh rate does not affect problem) My Macbook has 2 video cards: AMD Radeon Pro 5300M 4 GB Intel UHD Graphics 630 1536 MB It seems that any program that requires somewhat powerful video card uses my Radeon Pro video card has problems with lags. The problem also with anything that I assume has extensive graphics card uses. Browser tabs, when hovering them, some menus in settings on macOS, scrolling lags so much. I noticed the problems after I connected external display first time with display port (not HDMI) and I had like SUPER SMOOTH everything, even Blender. Of course, without external display I have no such lags and this is what shocks me the most. I mean I have 1080p resolution on external display and retina resolution on macbook - why would anything lag on such low resolution on external display? Now, if I connect Display, I have heavy lags on basically any program that requires good graphics card. If it matters, Macbook in vertical position, back side on the bottom, clamshell mode. Here are my settings for display: