yes, we have experienced Safari performance problem on ios 15 too. even worse on beta 5, using a game from https://www.pixijs.com/gallery https://tooncup.cartoonnetwork.co.uk/home/ it gets stuck at the entering game, while there is no problem on ios 14.

try to disable option "GPU Process: Canvas Rendering". we don't know why it's on by default on beta 4 and 5.

no, same as portrait, it becomes a thick bar after beta 6