I would like to get some clarification about the correct way to create limited users to access to my VPS user as WEBSERVER with Nginix.

I'm used to NOT install FTP and access via SFTP only. It is ok for every set up?

this is what I usually do from to create a limited user called "admin" that should be able to have access via SFTP to the folder with the website data

mkdir -p /var/www/mysite.com/
adduser admin
adduser admin www-data
chown -R root:root /var/www
chmod -R 755 /var/www
chmod -R 755 /var/www/mysite.com
chown -R admin:www-data /var/www/mysite.com/

It seems not to be the correct way, I always have problems with permission when I upload some files (for example with Wordpress in general). I would like to create an user that does work exactly as the one that the "provides" give to their client when they buy an Hosting service (that is a FTP, I would prefer SFTP access). It is for personal user, but I think that a limited user is a lot safer to use then the "root" via SFTP.