As luck would have it I just installed 64 bit version of X2a prod bout 2 weeks ago.
1. Is there any useful reason to keep X1, X2, both installed?
2. If not useful or needed? 
    Is un-install remove the existing Cakewalk support VST's and also VSTi's?
 
I do not have any crucial edited configurations needed.
 
Current plan was to do entire 32 and 64 bit versions, not using the older versions.
 
Thanks in advance!

It's not necessary to uninstall. It's entirely up to you.
 
If you DO uninstall, the uninstaller will prompt you at one point with a message along the lines of "The following component is a shared component, would you like to remove it". When you see this, click [No to all], otherwise it will remove things like the Plug-in Manager and the VST Scanner, V-Vocal, etc.

I would suggest you keep your X2 installations, for a while, just in case there are any issues or bewilderment in X3.
 
Bob Bone
 

One reason not to to rush to uninstall is you may have projects that rely on plugins no longer included in X3.  I'm planning on uninstalling X2 and reinstalling just the plugins I may still use before installing X3.

Ryan,
Excellent points you made.  Great tip on the NO answers...
 
Bob,
Also good point, no rush, just trying to NOT eat my 1 tera HD.
Bewilderment, that more describes my level with this system...
 
dubdisciple,
That never crossed my mind.  That would be a real pain.
Good idea on the plugins.
Thanks to you all!