I haven't overclocked a phone since my Droid Incredible. The Snapdragon 600 in the s4 is still a pretty good cpu, don't think it needs overclocking.
And nope, the radio in the s4 is complete garbage. Heck, just the other night I was at a friend's and his Note 3 was still pulling 4g with pretty good signal, and he has a pretty bulky case around his Note. Mine is "naked" and I couldn't get 3g, and when I had looked at my battery stats,I had lost signal completely intermittently. No need to really speak about the radios in the iPhones that were in the house, they were all on 4g... I mean it was so bad I couldn't even send a basic text message, it kept failing.
I'm on NG6, but found a method of root that has me flash an NC5 kernel, root it with towelroot, then flash the NG6 kernel back on. A bit more work to do, but it could be worth it. I forget how just about every single app has an ad, and I miss some of the lighter mods that Xposed gave me.