grouper is WiFi only, if you are talking about implementing mobile data in this ROM.
From my experience, there is only one ROM based on Android 7.1.1 without freezes and lags, the AOSP one from AndDiSa (see here https://xdaforums.com/nexus-7/development/rom-android-7-aosp-grouper-t3467514). I also would have stayed on this CM11 ROM, but the fact that it has been discontinued and the smoothness of the AOSP one changed my mind....
But it appears that n7 can't handle any other rom higher than 4.4.4.
...
From my experience, there is only one ROM based on Android 7.1.1 without freezes and lags, the AOSP one from AndDiSa (see here https://xdaforums.com/nexus-7/development/rom-android-7-aosp-grouper-t3467514). I also would have stayed on this CM11 ROM, but the fact that it has been discontinued and the smoothness of the AOSP one changed my mind.
Hi guys, I have decided to abandon the development of this ROM. CM11 has run great on my N7 but it's been taking me a lot of time patching the code.
I have now moved on and I am using AndDiSa's 7.1 rom and its performance is really good (on par with CM11) and it's getting monthly security updates as well.