Lenovo sells such a display. Built in mic, cam and speakers.

It’s also a usb c dock with a Ethernet port

DELL too, bought a 4k 24" conference monitor off a second hand site for £80. It's got a good quality pop-up webcam, too. Usb hub, hdmi/dp ports, Ethernet on the back. Connects and powers the laptop with a single thunderbolt usb-c cable.

Not sure about ppi and stuff, but works great for me.

any specific model you had in mind? when I'm looking at the Lenovo offering, the "built-in" webcams are protruding and if I pair it with 4k resolution I quickly end up at 1300 dollars (yoga pro)... for $1600 you get the 5k apple Studio Display.