stuck moving to whm ...

There is no version of cPanel that does not include the WebHost Manager. The product has always consisted of two interfaces, the WHM for the server administrator and cPanel for the domain-level user. What it sounds like is you are moving from a regular cPanel user account to a reseller account that gives you access to the WHM as a reseller.

As manokiss mentioned, as long as mod_userdir is enabled on the server (it is by default) and mod_userdir protection has not been configured to prevent it (this would be done by the server administrator, but by default there is no restriction; if in doubt, you will need to ask the server administrator), then previewing the site by IP address will work:

http://server_ip_address/~cpaneluser

where server_ip_address is the IP address of the server hosting your site, and "cpaneluser" is replaced with the username you log into cPanel with. The tilde is important and should be entered before the cPanel username; it tells Apache to "look in the home directory for this system user."

There is no way to completely avoid all downtime when you change DNS records to point to the new host. Due to the way the Internet DNS system works, it can take some time (from 24 to 72 hours, and sometimes more) for DNS changes to propagate, and this can make your site(s) appear offline in some locations while DNS servers across the globe update their caches.

 

To ensure a complete transfer of information, I would consider accessing cPanel on the previous service to generate a full backup of each account. If the freshly-generated, full account backups are provided to the new service provider they can, via "root" (i.e., Administrator) access, restore each cPanel account in full and reassign ownership to be under your control (so that the cPanel accounts can be managed via your reseller access to WebHost Manager).

Alternatively, if you provide your new service provider with the IP address and login information for the old cPanel accounts then the new service provider can attempt to transfer the accounts for you, using WebHost Manager via the following menu path: WHM: Main >> Transfers >> Copy an Account from Another Server with Account Password