The performance limiting features are actually not a real problem because 450-550Mbps is high enough bandwidth to fit the need of QoS options. I have 2x residential lines under this bandwidth (300/30 and 100/40) and not using any QoS. This is not a gaming device and no QoS will fix bad ISP anyway. I'm perhaps lucky the ISPs are quite consistent. About PPPoE + VLAN issue - I can't confirm or deny the information found online. Some say ~700Mbps, others ~900Mbps (for UCG-Ultra), there are also reports for ~700Mbps and full speed ~2.3Gbps (for UCG-Max). I guess,
@Jbennett360 will let us know soon. Hopefully it works well on their ISP.
About hardware similarities between UCG-Ultra and UCG-Max - I wouldn't be surprised if the PCB for Ultra has missing components used in Max. Two SKUs for GbE and 2.5GbE applications give users a choice. Nothing to complain about $130 Ultra version.