I use the WD drive and have a DJI P3S - yeah I know it's the old one
I will be honest and say that time isn't a problem for me so speed of transfer is not a concern of mine so I haven't done any specific speed/time tests
I can confirm though that with the Micro SD in an adapter, files from the drone will transfer flawlessly to the WD drive - how fast - fast enough for me!
You're not talking about vast amounts of difference in time between the method above and airdrop although as the file size increases the difference in time will become more apparent. Unless they've changed the file system with the MavicAir the biggest individual file you will have is 4 gig. If you shoot a long video in 4k it will be split into 4 gig chunks. With LF being able to handle 4k I always shoot in the highest res available (only 2.7k on P3S) and you can export at a lower res if you want to
You can also wirelessly back up your photos and video from your iThings to the WD drive so you've got everything in one place
LF will import video and stills from the WD drive with no problems