You need a faster Peplink for a connection above 400Mbps. The used chip cannot handle more. And as there is no Ethernet standard for 400Mbps, anything that can do more than 100Mbps has a Gigabit physical port. This is not unique to Peplink.
Depending on the other features you need, you might take a look at the Balance 20X, which supports 900Mbps Stateful Firewall Throughput.