The user-specific crontab files are stored in the /var/spool/cron/crontabs directory, where each file is named after the username of the owner. These files are not meant to be edited directly, but rather through the crontab command. The other options are either incorrect or non-existent locations for user crontab files. Reference:
Where is the user crontab stored?
crontab running as a specific user
Location of the crontab file
Where is the User Crontab Stored?