CGNAT is a menace to any low latency connection since now your route needs to jump through some NATed hops that may be under varying amounts of load depending on how large the translation tables are. Things get worse if connectivity has to be established by some middlebox as you have no idea how many hops it takes to go to the middlebox and you have no guarantee how loaded this box is. Using a public TURN server can be terrible for VoIP call latency.