STABLE version -- 4.3.9.248

[Admini]

I'm use 150% scale of desktop with recommended 1920x1080 & following keys --high-dpi-support=1 --force-device-scale-factor=1.3
With one monitor connected, browser element tooltips pop up like in the picture ..
When I connect a second monitor, they and with them the browsers main menu start to displaying only on the second screen, while the browser itself is only on the screen of the first monitor. And pop-ups of extensions begin to align not to the right edge of the extension icon, but to the left, and are also most often located (partially) on the second screen.

Have you tested this with Chrome.
May be a Chromium bug.