Have you tried turning off app optimisation? I did this last week on my S8 following the advice from another member. The lag is completely gone, its great now.
Go to device maintenance>battery>unmonitored apps. Now add the DJI app to the list. This i assume lifts the restriction on the app using a certain amount of power.
Thanks for this tip. Works well. Lag on my S8 was acceptable but annoying more than anything. This did the trick.