I will want to use port 587 as a secondary port. Am I suppose to follow the instructions for 'addtional transport'? Are there standard setup here for adding port 587?
PFA doesn't need anything setting up for this - it's entirely a Postfix issue. Some distros (eg Debian) set this up automatically, if not then you'll need to add an entry to master.cf
Checking one of my boxes, Debian installs these in master.cf :
smtp inet n - - - - smtpd
submission inet n - - - - smtpd
As I read the man page for master.cf, it looks like this is sufficient to start an SMTP server listening on the Submission port on all interfaces - the first field being of the form "port".
The options available to smtpd are described in it's man page - and are mostly the same (IIRC) as those you can use in main.cf.
Port 587, aka the 'submission' port, is NOT a 'transport', it is simply a TCP port used by postfix to allow mail CLIENTS to TLS authenticate to send emails.
A transport in postfix is a completely different animal: