I just want to create multi-website, i read some links to guide me create a subfolder and create symbolic links of app,pub,lib,var and copy index.php & .htaccess from root folder to a subfolder.

Here where i can create a subfolder Root folder or Pub folder?

This guide leads to create under Root folder => https://meetanshi.com/blog/setup-magento-2-multi-store/

This guide leads to create under Pub folder => https://magento.stackexchange.com/a/198257/57334

Which one should I follow?

And how to add my localhost URL to my Nginx configuration, most of the documents and online links teach only live URL.

My single store Nginx Configuration :

server {
listen 8087;
server_name gomart;
set $MAGE_ROOT /usr/share/nginx/html/gomart;
include /usr/share/nginx/html/gomart/nginx.conf.sample;
error_log /usr/share/nginx/html/gomart/gomart_error.log;
access_log /usr/share/nginx/html/gomart/gomart_access.log;
set $MAGE_RUN_TYPE website;
}

upstream fastcgi_backend2 {
server 127.0.0.1:9000;
}

I just want to create multi-website, i read some links to guide me to create a subfolder and create symbolic links of app,pub,lib,var and copy index.php & .htaccess from root folder to a subfolder.

Here where i can create a subfolder Root folder or Pub folder?

This guide leads to create under Root folder => https://meetanshi.com/blog/setup-magento-2-multi-store/

This guide leads to create under Pub folder => https://magento.stackexchange.com/a/198257/57334

Which one should I follow?

And how to add my localhost URL to my Nginx configuration, most of the documents and online links teach only live URL.

My single store Nginx Configuration :

server {
listen 8087;
server_name gomart;
set $MAGE_ROOT /usr/share/nginx/html/gomart;
include /usr/share/nginx/html/gomart/nginx.conf.sample;
error_log /usr/share/nginx/html/gomart/gomart_error.log;
access_log /usr/share/nginx/html/gomart/gomart_access.log;
set $MAGE_RUN_TYPE website;
}

upstream fastcgi_backend2 {
server 127.0.0.1:9000;
}