Odroid N2?
The UDM Pro[0] has a quad-core Cortex A57 CPU running at 1.7GHz, according to the spec sheet I'm looking at right now. It has 4GB of RAM.
The ODROID-N2+[1] has a quad-core Cortex A73 CPU running at 2.4GHz. It also has 4GB of RAM.
The UDM Pro is like half the performance of the ODROID-N2+, accounting for architecture and frequency differences, so... I'm not sure what you're getting at?
The ODROID should be more than enough to handle a gigabit connection if the UDM Pro is even halfway capable of it, from a power perspective. Connecting more ethernet ports to it without an exposed PCIe connector is going to be clunky, but that's not the issue you pointed out.
[0]: https://dl.ubnt.com/ds/udm-pro
[1]: https://www.hardkernel.com/shop/odroid-n2-with-4gbyte-ram-2/
It should also be self-evident, but I also need more the one interface to route traffic to two seperate networks, ignoring that the requirement is actually to load balance multiple systems to a internal 10gb/s network.
The USB is nowhere near what you need to run a 10gb/s or even a 2.5GB/e (based on my experience with other ARM hardware).
(source: I benchmarked my N2+. It'll route and NAT 1 GBit quite leisurely.)