Whenever you're buying a smartphone you must always look for the processor because that is the thing on which whole performance of the phone is decided so whether it comes to camera or anything your desire will be fulfilled.

So, as your looking for the best camera phone you must not always go for huge megapixels as the camera quality is dependent on their lens not on megapixels so you must check these specific thing and the most important thing you must check the fps video which the specific phone is providing you must make sure there is no lagging in it. As in my opinion, You must compare all devices and then go for it or you can even watch some YouTube videos which are also giving you best comparison of camera and every feature of devices so you can buy your best so as in my opinion, check the lens of the camera whichever the device is providing check the reviews of that device who ever have bought it earlier do some researches on it and then go for it Don't just ads of particular devices fancy you. As it is just a marketing technique provided by every device. So in my opinion you can go for oppo smartphones which are providing pretty good camera with AI feature in it which does half the work for you whenever you're clicking a picture and it is quite budget friendly too. And if you proceed more with a higher budget you could go for Google pixel who has the best camera with brighter aperture and pretty decent zoom. 

Aperture plays an important role in camera as it provides specified light for decent clicks and also the zoom as there are lots of devices who are providing us with 2x optical zoom and even 3 which gives us pretty decent shots which comes in iPhone devices and oneplus devices so the camera of the device not only depends on megapixels don't just go for huge pixels go with overall performance of the device as processors play an important role in smartphones so read some reviews Do some researches and then buy it and Don't just big brands fool you as there are lots of smaller brands who provide you the best features which big brands doesn't so this is my opinion while buying the best camera phone.