Hello, We have setup a server from your https://www.howtoforge.com/perfect-server-centos-7-x86_64-nginx-dovecot-ispconfig-3 .. everything is up and running good. We do get some strange 500 Internal Server Errors but we are on those and trying to fix them. One thing though. We will use this for clients etc and its great to setup a FTP acount for those clients that need it. But it would also be great if we could have a good "Master FTP" account with permission to upload and change in all folders. And when uploading getting the correct permissions etc. So we dont need to add each and every website to our FileZilla to work.
Short answer: It's not possible because of file and folder permissions. It would only be possible if all folders would be owned by same user.