If it's newly updated less than two weeks ago I would be patient. The process of syncing and indexing can cause hitching and stalling. Messages/Photos syncs can take a very long time. The very low level indexing performed can also take a long time. For future reference restoring from iCloud is settings and app data. The OS and apps are all new downloads, there isn't a benefit to not restoring from iCloud if it exist, if you don't mind the hassle of redoing everything it doesnt matter though because sync'ing and indexing still occurs.
Generally I don't like using too much information people give on here that is based on their personal experiences due to its subjective nature. For example, FOR ME Widgets have virtually no impact on performance.
But again that is just my experience and only applies to me. Someone else could have a widget that is causing issues and when they disable them their specific problem is fixed.
There are over 380 live processes running on my iPhone while it's currently locked. There is a good chance someone elses experiences just won't reference yours. Touch response gets top priority to always feel responsive. If its lagging there is bottleneck the OS is reallocating resources for due to high CPU, memory and/or storage pressure. Symptom is too common to precisely pinpoint across all devices.
Swapping between two apps that there aren't resources to allocate both can easily cause lag because you'll "feel" hitching around 20 millisecond of lag however it can take 50-5000+ millisecond to reallocate resources depending on whether the app was compressed in memory or terminated from memory...
If you have a Mac I would recommend getting Xcode to use "Instruments" and log 'activity manager' when using the phone. Note the time of the recording when/if you experience lag, something MIGHT stand out when you review the log. It's far from perfect because a lot of task can fall under one process but it can at least point you to something a bit more specific for your problem.
