In order to use the first two options
Limit The Amount of Accounts [ account ] can create by account type.
Limit The Amount of Accounts [ account ] can create by number to accounts.
as listed in: Reseller section & Edit Reseller Privileges/Nameservers, one has to understand the wording is incorrect -- it should say &packages&.
With that said, a Reseller cannot sell a package that has not been setup. So who sets up the package? It works great when a Reseller is reselling packages for the Hoster, but when selling their own packages that type of restriction doesn't work so well. The Hoster would continually have to be checking each Reseller to see who has created what package. By default, WHM allows &unlimted& selling of any package which is why the &zero& is shown -- zero means unlimited in WHM-speak.
I would guess that as long as you tell your Reseller they have to create all the packages they are going to sell (ASAP of course), then you can go back and set the limits accordingly. This does place a lot of restrictions though, for each Resellers.
For what you want to do, you would create the packages then, as each Reseller signs up, create an account for each one. It does get confusing though as you will find.