I just spoke to EuroWings, and they claim I only get 1 23kg bag.
The agent I spoke to was not aware of the "Most Significant Carrier" rule and stated that since I will be starting my journey on Eurowings that their Baggage policy was the one that would be enforced.
Interesting, when I look at my e-ticket from UA, it only says only 1 bag on the DUS-LHR-EWR-MYR flights.