". . . what would be the impact on VOIP and regular clients traffic? "
Usually not, but there a couple of potential conflicts.
First, one possible area of impact, again unlikely, would be using jumbo frames might use up buffer RAM sooner than standard size Ethernet frames, which might impact even non-jumbo sized frames. (Not too likely on a Nexus, more of a concern on low end edge switches.)
Second, again unlikely, assuming your edge ports are high speed, a preceding jumbo frame (or frames) will delay a following VoIP frame longer (as jumbo size frames take longer to transmit). (For this issue, if you think QoS will mitigate, it will, but not totally. Again, though, for high speed [e.g. gig] ports the extra delay is generally not an issue for VoIP. If you're concerned about extremely low latency apps [i.e. the type where you need to use cut through switching], then it might become an issue.)
