How do you deal with lots of addons.
 

I was planning to use a compilation addon from this website. However, I only want to use it for one character (PVE). On my other character I prefer the default UI for pvp. Is there any way to easily handle addons?

You can try this:
http://www.wowinterface.com/download...trolPanel.html

You can also enable/disable addon on a per character basis in the addon menu at the character select screen.