When you create an account, Windows asks you if you want to make the folder private.
If you missed that one, you can use NTFS permission to restrict access to folders/files. In this case, you'd be admin with full access to everything and everyone else would be limited user. If your partition is NTFS (go to my computer to check), it can be done. Right-click a folder to limit access, properties, security, edit, add a limited user account, check deny everything, ok, ok.
EFS is nice, but I had problems with it when doing a clean Windows install & lost the credentials. Needless to say, I couldn't access everything on the drive. A better portable way is to use an encrypted folder. There are free tools to do that. Cryptainer, gnupg, etc.