Droplet hostname = mail.company.com whereby
company.com = landing biz page and
abc.company.com = for [client abc] and xyz.company.com = for [client xyz] etc.

Q1) Should my reverse dns be company.com OR mail.company.com?

Q2) Do i need to create a => A record : [mail] [droplet IP] if my reverse dns is mail.company.com ?
e.g. reverse dns=hello.company.com : A record : [hello] [droplet IP]
even if hello.company.com is not serving any webpages

Thanks in advance.