I know that the official case is not out yet, so i went head and i got one from ALI, here the result of a shallow dive at 9mt.
https://m.youtube.com/watch?v=w_36n5rDQOw

is there a way to improve it, while i wait/prey for DJI for realise an official dive case

There's nothing you can do until a proper housing is available.

Take a look at the last comments in this thread for the X5. Even the original "basic" case didn't solve the stitching issue. And I'm sure it depends on FW too.

https://waterpixels.net/forums/topic/2592-insta360-x5-underwater/

Yikes! That doesn’t look good! I’m sure it will be better when a proper case if available.