4k monitor

Hi community.

I want to purchase a new monitor. I've never had a 4k monitor, so I'm considerate before buying one.

I'm confused if the graphics on a 4k resolution are tiny? So for example if my resolution is 4k, and my PS canvas is 1000 x 400 pixels, will it be at 100% like on a 1920 x 1080 resolution screen, or will PS be at 50% when it creates the canvas, and I need to keep on zooming until it gets to 100% so I can see the canvas size at 100%?