APT-x is very good, low latency codec. It's been around a long time and is not marketing fluff. Some AAC codecs are also very well made for specific purposes. Opus is too high latency for headphones.
The lowest number I can find for "low-latency Apt-X" is 32 ms end-to-end over Bluetooth. Opus frames default to 20 ms wide but can be configured as small as 2.5 ms, so I don't think it's going to slow things down very much.
Opus is specifically designed to be low latency. I'm not sure where you got the idea that latency would be a problem. Of all the lossy codecs, there isn't much that is faster.
