I recommend updating all your apps if you’re the sort of person who has disabled automatic updates and forgets to do it manually. Running older apps on the new release could cause glitches and issues.
It’s also a good idea to make space before installing a new update. The run-up to a new iOS release is a good time to get rid of any apps that you’re not using anymore and that’s a good and pain-free way to free up some space.
You need at least a gigabyte to carry out an update, and ideally, two or three gigabytes of free space is best because that will speed up the update process. Any less than this, and your iPhone will have to do a lot of housekeeping to make that space (iOS updates can delete apps to make space to install the update and then redownload the apps, but this makes the update take a lot of time).