[Q] nexus 7 question topic

Ok i am very new to this , this may be answered elsewhere but i couldn't find it . after updating my nexus 7 to lollipop the update practically ruined my nexus , it has never ran so terrible. I have rooted it since and i am looking to see if a different rom/operating system is better. does anyone with a nexus have any suggestions. I have used cyanogen years ago on my htc evo and liked it but what you someone with better experience suggest. also it is asking to update to android system 5.0.2 and i am not sure it i do that if it will take my root access away....i am guessing it will ?

thank you , and sorry for being such a noob