How about NanoPi Neo Air?
With software encoding I think you could do far better than with hardware encoding with a few tweaks, since you have low latency bidirectional communication. With a proper bidirectional protocol you can deal with packetloss far better than standard methods. For instance you can increase FEC depending on packetloss, re-request MBs as long as the display deadline hasn't been reached, without acknowledgement have the encoder not use MBs as a reference etc.