Apple just released their fourth beta of iOS 12.4 and now we have a speed test video of iOS 12.3.1 vs iOS 12.4 beta 4.
In the video below the two versions of iOS are run side by side on the iPhone 5S, iPhone 6, iPhone 6S, iPhone 7 and iPhone 8, lets see if there are any speed improvements.
If you want to skip to a specific device the iPhone 5S starts at 00.25, the iPhone 6 09.20, iPhone 6S 17.23, iPhone 7 24.06, iPhone 8 30.42.
As we can see from the video there do not appear to be any major speed improvements in the boot up times of the various devices and also no major improvements within the apps.
Source & Image Credit iAppleBytes