Yes, it will install automatically, but for most, it won't install immediately upon release Tuesday, April 11th simply because the Microsoft Servers won't be able to handle it. In addition, it is possible to install manually. See the discussions at the top of this forum about the Creator Update release. Also, if you'd like to make sure that it doesn't install immediately upon release, and you've running the PRO version of Windows 10, you can temporarily delay the update install by changing this setting: Click on the "Start" button, then the "Settings" icon, then the "Update and Setting" link, then the "Advanced Options" blue link, then the place a CHECK mark in the "Defer Feature Updates" box.
To install manually, you can either run the "Update Assistant" from the "Microsoft Windows 10 Media Creation Tool" page, or by downloading the Windows 10 ISO, mounting the ISO or burning the ISO image to DVD or USB, then running the Setup.exe file.
As to the additional features, or pros and cons provided by the Creator Update, there are lots of articles about it on the net. One GOOD feature I'm happy to see will be additional options for delaying Windows Updates and Upgrades. Here's just one article:
But I don't believe we really have a choice whether the update will be installed on Windows 10 machines. Of course, you can move to a different operating system but if you want Windows 10, you'll eventually get this update/upgrade.
Hope this helps......................