For starters, you should really read this article. Many of the things being said here are also written here:
I don’t specifically recommend any plugins to remove. I said it before and I’ll say it again: there is no way which reduces CPU power guaranteed.
Some people use a single hosting account to host dozens of different websites. While that’s perfectly possible with addon domains, using three hosting accounts and spreading the different websites across the three accounts effectively gives you three times the CPU power for all websites.
As for how to migrate the websites, just download the files and database from the website on account 1, remove the domain from account 1, create account 2 with the domain and upload the files and databases to that one.
Because apparently you reach the limit at that time.
No, I can’t. This paragraph explains why:
Finally, let’s not discuss this in two topics at the same time. Let’s merge the discussions in this topic: