Game Tech Wiki has everything you'd ever want to know about CRT shaders
(emulation.gametechwiki.com)
It depends. Graphics weren't spiky pixels as you can recall. That produced a far softer image, aside from scanlines and all the other stuff.
By now I can hardly play retro games from that time without shader, since the impression is auch a difference.
And I always was a pc player (from 8086/8088 on) and my consoles from mega drive on always used scart.
Still.