The DNS settings have nothing to do with your VPS or your Apache vhosts. DNS just 'points' to a numeric IP. The NameVirtualHost (vhosts) directives will do all the work.
As far as your vhosts:
On a managed VPS (one with a control panel) you should always use the control panel to add new domains, as it will do the work perfectly. I don't know SolusVM, but in Plesk v 10, you would use the Websites and Domains tab and 'add a new domain'. It will lead you through setting up all the items needed to provision that Domain on your VPS. That is to say, it will add the folders necessary, and make all the modifications to the Apache configuration. Sub-domains are virtual hostnames within a Domain. If its a Centos VPS, the files will likely be added under /var/www/vhosts/domainname.tld/httpdocs and /var/www/vhosts/domainname.tld/httpsdocs
All the filesystem structure and layout was done to enable hosting multiple domains the way the system looks for them. Don't fight the machine!
I have 3 VPS's and, even with my level of experience, I still let the control panel do all the work. Besides if you muck about and break it, you will have a hard time getting the hosting support desk's help fixing it.