Is audio and video slightly out of sync when iPhone is used with a Bluetooth earphone?
A quick Web search reveals this article, which claims to have done quite some good research on the topic:


AirPods Latency



  Disappointingly, and contrary to what I had hoped, AirPods have the worst latency of everything I've tested so far. For context, a wired connection achieved latencies of 61ms playing Tapt, and 106ms using the iOS keyboard. The AirPods had latencies of 251ms and 296ms respectively, in the same tests.
  
  Even the worst offender in my previous test, the JBL Flip 2, achieved significantly shorter latencies (218ms and 258ms, respectively). In contrast, my £30 Brainwavz Bluetooth eabuds achieved respective latencies of 199ms and 249ms in the same two tests.
  
  I would theorise that perhaps the need to ensure both AirPods play sounds in sync necessitates some small amount of additional communication, and thus latency. Hopefully it's something that could be improved with software updates in future. Of course any wireless technology is going to be slower than a contemporary wired solution, and I didn't expect the AirPods' latency to be on par with wired audio, but their failure to beat the latency of much cheaper Bluetooth earbuds is a downer.


However, it could be taken with some grain of salt as it an almost 2 year old article and software updates may indeed have fixed the noted latency issue. As is a general trend, the performance and bug fixes are rolled out over period of time, subsequent to release of any new hardware by Apple. The article was written about time the AirPods were newly released.