20H2 is a fairly minor update and will not remove any installed apps or user data. Your Windows system will simply have some features added. The 20H2 update has also previously been tested over time time by a large group of volunteer users called Windows Insiders so should be quite stable. Despite all of this, whilst it is generally good practice to keep your system up to date with all update it is also advisable to back up any important data before running the update. You may do this manually just copying selected files and folders, by using Windows backup or by using a full imaging utility such as Macrium Reflect (free!)