I have been thinking to buy a external monitor for my laptop. It has 2graphics interfaces, Intel HD graphics 620 & AMD Radeon R5 M430.
I'm confused if the intel GPU will support high refresh rates since it's the default display adapter.
I would really appreciate if you guys can help me out with this.
Rather than focusing on what the intel GPU may support, in the end what you need to know is what your laptop supports...
Intel HD 620 supports HDMI 1.4 4096x2304@24Hz and displayport 4096x2304@60Hz ... playing with the resolution (lower resolutions) this may allow more bandwidth to increase the refresh rate... for instance, you might achieve 120Hz (144Hz if you're lucky) if reducing the resolution to 1080p.
But... that is what the GPU supports in general terms... however, the laptop manufacturer might have set limitations to the video outputs... Let me share an example: I have seen vendors limiting HDMI video outputs to just 1080p 60Hz resolutions (I still don't understand why they do that).
If you really want to know what resolutions and refresh rates would be supported by an external display, you need to review your laptop's documentation or ask the laptop manufacturer...