Hi,

As far as i know, DO presently doesn't have any WHM / Cpanel option. They provide you bare bone setup of different OS like Linux based CentOS or Ubuntu and such..

Once you deploy a VPS, you may purchase seperate cPanel / WHM license from anywhere else and install that on the VPS of DO which you can create from their panel..

For cPanel, its better to have a plan with 2GB or more RAM (as per cPanel.net specification) along with CentOS x64 (6.6 or 7) and you may follow following tutorial to install cPanel in DO..

https://www.digitalocean.com/community/tutorials/how-to-install-cpanel-on-a-virtual-server-running-centos-6

Since DO is barebone setup so support of cPanel can be obtained from cPanel.net as its a paid software. Priced around USD 15 / Month..

Secondly, if you need to move to a bigger plan, all you need to do is,

1. Shutdown the Droplet (VPS is called Droplet here)
2. Then take a snapshot (make take a while depending on how much data you have)
3. Then recreate a droplet with a bigger plan
4. Restore the snapshot..

Read this -> https://www.digitalocean.com/community/articles/how-to-resize-droplets-using-snapshots

Possibility of Most of the question you have is answered many times here, so try to Google for answers with "Site:" search option in digital ocean domain to look for them for faster solution..

Thanks..