Is 4K worth it on a 27-inch screen?

Yes for sharpness: 4K at 27 inches gives very crisp text and fine detail for work and games. The trade-off is that you need a powerful GPU to run games at native 4K, and you may want display scaling so text stays readable.

Can I connect a laptop with one USB-C cable?

Yes. The USB-C port carries video, and on this class of monitor it typically also charges a compatible laptop, so one cable handles display and power. Check your laptop's USB-C power delivery rating before relying on it.

Does it have built-in speakers?

Yes, it has built-in speakers, so you get basic audio without separate desk speakers. They are fine for calls and casual use but thin for music and games with heavy bass.

What can I connect to it?

It has HDMI, DisplayPort and USB-C inputs, covering a PC, a console and a laptop. That makes it easy to switch between a desktop and a work laptop without replugging cables.

Is it good for competitive shooters?

It is better suited to sharp, detailed games than to fast competitive play, since 4K at 27 inches is hard to drive at very high frame rates. Check the listed refresh rate and adaptive sync support before buying for esports.