It seems from recent testing that IOS 14.5 betas 1-3 all have issues with system lag and freeze. This happens across the platform and in specific in apps which have animation, such as adds, and live video feeds.

The root cause seems to animation and live video feeds. The problem does not occur as noticeably with buffered video downloads such as YouTube.

The device as a whole becomes laggy and responses are delayed. Live video feeds are greatly delayed.  Over time the device may eventually freeze.

Closing the app experiencing the problem  can help but the same problem reoccurs shortly after reopening the app and initiating the live video feed.

I will submit a bug report to the Apple Developers Portal today.

It might be wise to hold off on installing IOS 14.5 beta or updating to IOS 14.5 upon release until the bug is resolved.  

*** Update ***
Based on some further testing it appears that IOS 14.5 beta is experiencing severe thermal throttling due to irregularly high processor usage when SpriteKit or something similar is used for animation and graphic rendering.  
I was able to replicate the the thermal throttling using rapid image subsitution, i.e. updating the indicator images.  

It appears in my test with a thrown together Xcode test app to not be related to video rending and transcoding but exclusively to the rending of images in quick succession.

The caused of the lagging and freezing may be the onscreen indicators, map, histogram and/or orientation views.  As this is a pervasive issue accross many applications I believe that it is an Apple issue.

It seems from recent testing that IOS 14.5 betas 1-3 all have issues with system lag and freeze. This happens across the platform and in specific in apps which have animation, such as adds, and live video feeds.

The root cause seems to animation and live video feeds. The problem does not occur as noticeably with buffered video downloads such as YouTube.

The device as a whole becomes laggy and responses are delayed. Live video feeds are greatly delayed.  Over time the device may eventually freeze.

Closing the app experiencing the problem  can help but the same problem reoccurs shortly after reopening the app and initiating the live video feed.

I will submit a bug report to the Apple Developers Portal today.

It might be wise to hold off on installing IOS 14.5 beta or updating to IOS 14.5 upon release until the bug is resolved.  

*** Update ***
Based on some further testing it appears that IOS 14.5 beta is experiencing severe thermal throttling due to irregularly high processor usage when SpriteKit or something similar is used for animation and graphic rendering.  
I was able to replicate the the thermal throttling using rapid image subsitution, i.e. updating the indicator images.  

It appears in my test with a thrown together Xcode test app to not be related to video rending and transcoding but exclusively to the rending of images in quick succession.

The caused of the lagging and freezing may be the onscreen indicators, map, histogram and/or orientation views.  As this is a pervasive issue accross many applications I believe that it is an Apple issue.