Noise after zooming is common because generally smartphones do not have optical zooming and also it depends on the ISO levels and mega pixel of the camera.
What do you mean by laging. I don’t think this phone should lag until otherwise rom is very low or in some special circumstances.you can use micro sd card if rom is getting low as you have stated you have installed a lots of apps. Phone can also lag if RAM gets low , Remember this phone has 4gb DDR4 RAM , may be there is some bug in the software I would recommend you to use a software to boost the ram like DU BOOSTER OR CC CLEANER.