Poco X3 user here
Front Cam, fine in day light, blurry pics or smeared details in indoor and low light.
Main Camera: Great in Day light, good indoor, but in low light, all light sources e.g brake lights, street lights scatter light around (Idk whether I should call it fringing or lens abbration) .
Ultrawide: Best midrange ultra wide camera, great in daylight, better than 8MP ultrawides in low light,
Macro: Okayish at its best
Performance wise: it is quite inconsistent, sometimes it'll go for a week without any hiccup then suddenly it'll develop a lag or stutter or overheating for now reason which sometimes a reboot would solve and sometimes when the MIUI system app causing it finishes its work only then it'll resolve.. UI runs at 20-40 fps so 120hz screen is just a waste of battery and less smooth than 60hz snapdragon 665 devices.
Battery life is very inconsistent as well, at its best it compares with 4500mah devices, at its worse it seems like phone has a 3700-4000mah battery.
Network performance isn't good either, indoors I've seen phones 5 year old 4G phones have better internet speeds. (my samsung C7 with Qualcomm X9 modem where as Poco has X15)
so yeah it was my first and last MIUI device (Oh wait I bought an M3 too which has similar issues)