I can help answer some of this.
is there a difference between putting "onclick" inside the element tag or using
jquery's delegate like the following example
Adding an 'onclick' attribute to an element has been deprecated in the HTML specifications. Using .live() and .delegate() it will take extra cpu, but it's worth it to keep your code valid and maintainable.
does it make a big difference selecting an element with a full path
like (#body #contentdiv #userstbl td.example)
or just typing (.example) ?
In your example if you just used the class name to locate the element jQuery would have to iterate over every single element in the DOM. This takes quite a bit longer than scoping the amount of elements it has to search to an id/element type.
It's always faster to scope your selectors to an id if possible. You can store it as a jQuery collection as well so your code doesn't have to re-do the work to select it from the dom againl, eg:
// you don't need multiple ids, each id should be unique
var $userTable = jQuery('#userstbl');
var exampleCell = jQuery('td.example',$userTable);