> Never had any problem connecting 3 different MacBook Pro's (across the years) to 3-4 different external monitors (Dell, LG, Samsung, etc) and to several projectors (including through a VGA adaptor and HDMI ones).

Consider yourself lucky.

> So for all of 2 seconds it takes?

Most times. But occasionally I've seen the OS seemingly get confused/stuck in the process. Flickering, moving windows into various locations on the screen, taking 10-15 seconds to get back to functional/usable.