And since I couldn't find much about the CPU, does anyone know how the IPQ8071A compares to the IPQ8074A like in the FritzBox 4060 at more demanding tasks like Wireguard / OpenVPN encryption? (That's also the reason I'm not considering the NWA50AX with MT7621AT)
It may range from "relatively straightforward" ('just' another ipq807x system) to "impossible" (secure boot fuse enabled and fully locked down bootloader), no one knows, until it lands on the desk of someone willing to work on it, case removed, serial console attached.
The specifications suggest that it may be supportable, the ZyXEL NBG7815 already is, but no one has looked into the NWA210AX, yet.
It's the same SOC family, you can compare the specifications 1:1. The obvious difference would be the clock frequency, 4*1.0 GHz (factory overclocked to 1.38 GHz on the Xiaomi AX3600) for ipq8071a vs 4*2.2 GHz on ipq8072a and up - and you will feel that difference easily.