tom23
composer.jsoncomposer.lockpublic/assets/extend.php if you made changes to itconfig.php if you want to be lazy
Pretty much everything else can be recreated with a clean install and overwriting the above files with the backup. Some extensions might write files into storage but backing that folder up entirely makes no sense as it also includes cache and session files and other folders that aren't critical.
If you want to be 100% sure, so you can quickly restore in case of emergency, backup everything except:
